Sonnet I

From fairest creatures we desire increase,
That thereby beauty's rose might never die,
But as the riper should by time decease,
His tender heir might bear his memory:
But thou contracted to thine own bright eyes,
Feed'st thy light's flame with self-substantial fuel,
Making a famine where abundance lies,
Thy self thy foe, to thy sweet self too cruel:
Thou that art now the world's fresh ornament,
And only herald to the gaudy spring,
Within thine own bud buriest thy content,
And, tender churl, mak'st waste in niggarding:
   Pity the world, or else this glutton be,
   To eat the world's due, by the grave and thee.

As the opening sonnet of the sequence, this one obviously has especial importance. It appears to look both before and after, into the future and the past. It sets the tone for the following group of so called 'procreation' sonnets 1-17. In addition, many of the compelling ideas of the later sonnets are first sketched out here - the youth's beauty, his vulnerability in the face of time's cruel processes, his potential for harm, to the world, and to himself, (perhaps also to his lovers), nature's beauty, which is dull in comparison to his, the threat of disease and cankers, the folly of being miserly, the need to see the world in a larger sense than through one's own restricted vision.

'Fair youth, be not churlish, be not self-centred, but go forth and fill the world with images of yourself, with heirs to replace you. Because of your beauty you owe the world a recompense, which now you are devouring as if you were an enemy to yourself. Take pity on the world, and do not, in utter selfish miserliness, allow yourself to become a perverted and self destructive object who eats up his own posterity'.

See also the further commentary on Sonnet 1

The 1609 Quarto Version

FRom faireſt creatures we deſire increaſe,
That thereby beauties Roſe might neuer die,
But as the riper ſhould by time deceaſe,
His tender heire might beare his memory:
But thou contracted to thine owne bright eyes,
Feed'ſt thy lights flame with ſelfe ſubſtantiall fewell,
Making a famine where aboundance lies,
Thy ſelfe thy foe,to thy ſweet ſelfe too cruell:
Thou that art now the worlds freſh ornament,
And only herauld to the gaudy ſpring,
Within thine owne bud burieſt thy content,
And tender chorle makſt waſt in niggarding:
   Pitty the world,or elſe this glutton be,
   To eate the worlds due,by the graue and thee.

Commentary

1. From fairest creatures we desire increase,

fairest creatures = all living things that are beautiful.
increase = procreation, offspring. A reference also to the increase of the harvest, by which one seed of corn becomes many. There is a general presumption in husbandry that the best stock must always be used in breeding, otherwise there is an overall decline and failure in productivity. The fairest creatures are therefore the fairest cattle, the best plants, the most excellent poultry, and so on. Whatever in fact is as good as, or an improvement on the previous generation. Basically this is a farming or agricultarist metaphor. In his later years Shakespeare seems to have been interested in the nature/nurture discussion. There is the famous passage in Winter's Tale, which is probably relevant here, in which Polixenes instructs Perdita on the science of breeding flowers. WT.IV.4.79-103. (See the end of this page).

2. That thereby beauty's rose might never die,

thereby = in that way, by that means.
beauty's rose The rose was symbolic of all things beautiful. By reproducing itself it could, in a sense, become immortal.

3. But as the riper should by time decease,

riper = older, more mature, (person, plant, thing) more ready for harvesting.
by time decease = die in the course of time.

4. His tender heir might bear his memory:
tender = young, delicate, soft. (Often applied to young animals).
bear his memory - as an imprint taken from a seal; also with the sense of 'bearing a child', so that the heir carries on the memory of parents through the generations.
5. But thou contracted to thine own bright eyes,
contracted = being contracted to, under obligation to (in a legal sense). It also conveys the sense of compressed, curtailed, restricted. Cf. Ham.I.ii.3-4.
...and our whole kingdom
To be contracted in one brow of woe,

However it is difficult to see exactly what contracted to thine own bright eyes means, although the glossarists cite the example of Narcissus from classical literature, who died having fallen in love with his own beauteous reflection in water. The general sense seems to be that of one who is perpetually pre-occupied with his own concerns, looking upon himself, and being under contract to pursue his own interests. See further discussions Sonnet 1
6. Feed'st thy light's flame with self-substantial fuel,
Feed'st thy light's flame = provides sustenance for the flame that gives light. Candles, tapers and oil lamps were the only source of light in Shakespeare's day.
self-substantial fuel = fuel from its own body. Although the general sense of this line seems to be that of a fire or lamp burning up fuel, there are difficulties of interpretation. After all, how is a candle meant to feed itself, other than with itself? The suggestion is that the fuel should be renewable. It implies a criticism of the youth, who is intent on devouring himself and his future hope. See further discussions Sonnet 1
7. Making a famine where abundance lies,
famine - emptiness, starvation, lack of provision for posterity.
abundance - presumably a reference to the youth's rich qualities, in contrast to the famine which he threatens to create. Famines and glut were part of the usual cycle of life in the Elizabethan world. A poor harvest could mean starvation for many, as the storage facilities which we take for granted were unknown in those times.
8. Thy self thy foe, to thy sweet self too cruel:
Thy self thy foe = being an enemy to yourself.
to thy sweet self too cruel - by refusing to procreate, hence denying a future to yourself. 'You are being cruel to yourself in seeking your own extinction'.
9. Thou that art now the world's fresh ornament,
the world's fresh ornament = a fresh and youthful glory to the world.
10. And only herald to the gaudy spring,
only = most important, chief, unique.
herald = one who announces, a messenger. Shakespeare elsewhere calls the lark the herald of the morn, and the owl the herald of night.
It was the lark, the herald of the morn,
No nightingale: look, love, what envious streaks
Do lace the severing clouds in yonder east:
RJ.III.5.6-8.

gaudy = bright, colourful (not necessarily vulgar).
11. Within thine own bud buriest thy content,
content = substance. Also, probably, pleasure. GBE suggests that content also = semen, and probably there is here a secondary meaning of masturbation, self-pleasure, as opposed to the pleasure of procreation. SB mentions that Shakespeare exploits the possibility that rosebuds were phallic in appearance. (p.324. note to 12-13). Content(s) even today has the double meaning of a) happiness, pleasure, and b) that which is contained in something.
12. And, tender churl, mak'st waste in niggarding:
tender churl - probably a phrase indicating affection, rather than criticism, rather like 'silly fool', or 'yer daft idiot'. The context makes all the difference to such forms, which spoken angrily can be insulting, spoken tenderly are terms of endearment. churl countryman, rustic;
mak'st waste = creates waste; lays waste, makes a desert; spills semen.
niggarding = being miserly, stingy.
13. Pity the world, or else this glutton be,

this glutton = a glutton like this, i.e, such as I am about to describe, one who eats his own share as well as the world's.

14. To eat the world's due, by the grave and thee.

by the grave and thee. Presumably, a duty owed to the world because the grave is all devouring, and therefore to be fought; and a duty owed also to yourself, because it is in the nature of things that beauty should procreate, otherwise 'three score years will bear the world away', and so on. You purpose to be such a glutton as to consume both what the world and you yourself should have as a right. The construction is not noticeably opaque until one starts to analyse it.

Additional notes

A discussion of eugenics by Shakespeare - the nature-nurture controversy. From The Winter's Tale, IV.4.79-103.

 PERDITA Sir, the year growing ancient,
Not yet on summer's death, nor on the birth
Of trembling winter, the fairest flowers o' the season
Are our carnations and streak'd gillyvors,
Which some call nature's bastards: of that kind
Our rustic garden's barren; and I care not
To get slips of them.
P
OLIXENES Wherefore, gentle maiden,
Do you neglect them?
PERDITA For I have heard it said
There is an art which in their piedness shares
With great creating nature.
POLIXENES Say there be;
Yet nature is made better by no mean
But nature makes that mean: so, over that art
Which you say adds to nature, is an art
That nature makes. You see, sweet maid, we marry
A gentler scion to the wildest stock,
And make conceive a bark of baser kind
By bud of nobler race: this is an art
Which does mend nature, change it rather, but
The art itself is nature.
PERDITA So it is.
POLIXENES Then make your garden rich in gillyvors, And do not call them bastards.
PERDITA I'll not put
The dibble in earth to set one slip of them;
No more than were I painted I would wish
This youth should say 'twere well and only therefore
Desire to breed by me.