couple of things..
plant things that are in season for your zone.. many varieties of lettuce are spring plants.. broccoli and cauliflower are fall crops..i had trouble with cuke's my first year, second year it got so crazy i had to pull the cucumber plants out of the bed (they grew up into the ceiling and started wrapping around wires and stuff) - and i did not have time to hand pollinate them
have you tried planting by "moon phase"? some people swear by it.. i think i've had some coincidental luck regarding the moon..
it's going to take a few months for your plants to reflect the conditions of the growbeds, don't get discouraged..