Keep your Basil from blooming...

If you want your basil to look like this late in the summer:

you need to give them a watering of nitrogen, the first number in the three number system for fertilizer: N_P-K, N being nitrogen. Fish fertilizer works, but don't get it on any leaves you plan to pick. Compost tea will work also, giving the plants the choice of food. If you are fighting blossoms, keep them pruned off for more leaf production. Take all the flower stems off and feed with high nitrogen fertilizer and voila, you have beautiful basil leaves again.