The first year one of our employees planted a tomatillo plant, she got loads of blooms on a sprawling plant, but no fruit. Two mistakes here - first, you need at least two tomatillo plants to ensure pollination and second, be sure to provide support for the plants. Last year's tomatillos were grown in 10-gallon pots with cages around them. Two plants yielded about six pounds of tomatillos, ranging in size from two inches across at the height of harvest down to 1/2" marbles just before frost. The characteristic tangy flavor of tomatillos is best when fruits have filled the papery husk but are still green. Yellow and purplish tinged tomatillos are fine, but lack the tart flavor. 

Tomatillos require similar growing conditions as tomatoes and peppers - lots of sun, deep rather than frequent watering, and staking. Like, tomato plants, tomatillos should be planted deep. Consider planting bee-attracting flowers nearby to ensure pollination.