There lies the million dollar question, it really does depend on how hot a day its has been. I could say every other day as I live in the north, but you may live in the south where its hotter. I would check your baskets/containers everyday and see how many days it takes for it to dry out. In general, if its cool 2-3 days between waterings and if its hot 1-2 days. Seriously hot, every day. And if its raining, put your feet up.
The trick is to touch the compost until you train your eyes to spot drying out - if it feels wet, don't water. If its dry, water. If its moist, give it a sip.
Hope this helps...