It would help to know what type of plants your having trouble with
The lights must be very close to the plants, 2 inches is good... and left on for 14-16 hours a day. I use tube fluorescent bulbs, but I would imagine the same thing would go for CFLs.
Other things that can help ...
Put a fan in the room (not so it's blasting on the plants, just to create air movement)
Tickle the plants... run your hand over the tops a couple times a day so they bend a bit... this triggers them to make a stronger stem.
Too warm temps make them grow too fast ... 70F during the day is best, cooler temps at night can help slow growth.
If you're using fertilizer, stop, or cut back.
Be careful not to over water ... moist is good, constantly wet is not good for any plant. Let the top soil dry, and the pot get somewhat light, then thoroughly water.
Tomato plants can be potted up into deeper containers, tall plastic cups work well. Poke a few holes in the cups and plant them as deep as you can. Roots will develop on the buried stem, making a better plant.
You can plant them deep in the garden too, removing the bottom leaves... so don't worry too much about them being long and lanky, as long as you can manage them til planting time...
