Should my skateboard trucks be tight? or loose?

im working m=on my ollie, my skateboard trucks are really loose so that i can turn better. i skate around alot and work on my ollies in a tennis court, but they really suck. Should i have tight or loose trucks then? i need to turn alot when skateboarding but they seem to ruin my ollies. it i tighten my trucks, how ddo i turn then?