Hey, I'm a beginner :-) but I also learned that you want to cut the leaves before they 'bolt'. If the plant gets stressed generally due to temperature, drought, overcrowding, etc., it starts to seed and flower = bolt. It also causes the lettuce to taste bitter. I read that if your lettuce plants bolt, it's probably best to heap them into your compost pile and start again.
That must be what happened to my basil last year! It grew tall and flowered and did not produce the lush basil leaves I was expecting. On that note, we caught a segment on the Katie Brown Workshop program and watched her & her pal build a tiered herb garden that we may give a try. They used a wooden stair risers and screwed in wooden window boxes. Here is a link to her instruction page: