Tilling or forking won't help in a lot of cases because you are just messing with the same crap soil. You'll need to add something to your soil to improve it.
Builders sand {slightly big grains that beach sand} is good for heavy clay soils.
Soil that drains too fast needs some clumpy compost added to retain some of the moisture.
We used to rent {now we own} a portable cement mixer and do a 50/50 mix with the current soil and light compost. Dig out the area you want to prepare and then throw 1 shovel of soil to 1 shovel of compost in. Use that to refill the area you just dug up. We do this every year with the help of the neighbor kids.
