If you already have seedlings that are stretched and look weak you can either:
A) Re-pot them up to about an inch under the bottom leaves, the buried stem will become roots. And get more light

or

B) Splint them up with something, a soda straw split vertically wrapped around the stem works wonderfully for holding up a wimpy seedling. Still, get more light, CFLs like 2" away from the plants.


Also, if you get an oscillating fan and point it so it blows lightly on the plants, it will strengthen the stems a lot. Oscillating fan = must have.

Note: Don't use the fan when they are just baby seedlings, they need moisture then. Wait til they get their first true leaves.