In short, the advice for beginners is you want your mast rake to be 20'5" from fully raised halyard to the center of the transom curve, and you want your rig tension to be 22 on a Pro Loos Gauge at that mast rake for 15 knots. If your jib halyard has a rack with 5 teeth, then you want this to occur when hooked on the middle tooth. Then each tooth is the proper tension for a wind range; 1=5-8, 2=9-13, 3=14-18, 4=19-22, 5=23+. These are guesses though, the real way you assess rig tension is with the sag in the jib luff. You put an elastic cord on the bottom of your forestay so that it is always taught, then you look at how much gap there is between the jib luff and the forestay when sailing close-hauled. It should be 1-2". More, tighten your rig. Less, loosen it. 

The most important thing of course is to sail with a balanced helm. You should be able to let go of the tiller and have it not go anywhere, and you should hold it very lightly with just two fingers so you are more sensitive to when it is pulling or pushing. If it is pulling, you are heeling to leeward. If it is pushing, you are heeling to weather. If you are *sure* you are flat (i.e. don't just guess), and it is still pushing/pulling, then your rake is off. Rake back to get rid of push, forward to get rid of pull. Bottom line is that if there is load on your helm, then your rudder is a speed brake. If you don't get up to speed, you won't point well.