Expanding on what Bill says... I have baked bread with sourdough starters for a while now, and I found that establishing an active starter takes time and patience. My suggestion is that you start off feeding the starter with very small amounts, and build up from there. What I do when I'm trying to establish a starter (revive one that has been in the fridge unused for too long) is to start by replacing 1 tablespoon of the starter with 1 tbs of flour and around 3/4 tbs of water (I aim for 100% hydration). Leave it at room temperature, and repeat that every 8 hours for 1-2 days. Then I double that amount of flour and water for another day or so, always replacing the same amount of the established starter. Then I go up to 1/4 cup of flour and so on until I have a really active starter. Jumping right up to 1 cup of flour with a brand new starter doesn't really give the starter a chance to establish. For a new starter, I usually aim for around 3 weeks before I use it. For a starter that I'm trying to wake up, a couple of days is all it takes.
I've noticed that the amount isn't as precise as yeast. A general rule of thumb is to replace 1/4 tsp of IDY with 1/4 cup of starter.
Hope that helps.