Set halyard tension - Pull sail up hard enough to remove 95% of the horizontal wrinkles along the luff of the sail for a laminate sail, and for a Dacron sail tension halyard enough to just barely remove all the horizontal wrinkles.

Set Jib/Genoa leads - Use these guidelines for proper lead location.  When the sail is trimmed in, the leech (back edge) and foot (bottom) should have approximately equal tension on them.  With an overlapping genoa, the sail should hit the spreader tip and the shroud base at about the same time.  Another good guide are luff telltales along the luff of the genoa.  The telltales should stream so that the upper tell-tales break slightly ahead of the lower telltales.

Sheet tension - For a genoa trim in so that the leech of the sail is about 2"-6" off the spreader tip.  This will vary greatly depending upon the type of rig and boat, length and number of spreaders, track locations and cut of sail.   For small non overlapping jibs with battens, trim until the battens point straight aft.

Leech and foot lines - are only used to remove the "fluttering" of the sail along these sail edges, not to "shape the sail" or "bag it out for light air".

Fine tuning your jib leads - In general, moving the jib leads aft depowers the sail and moving the jib leads forward adds more power to the headsail. 

By moving the lead aft, you are adding more twist to the top of the sail which allows the wind to "blow through" the top of the sail plan.  Also, by adding sheet tension you will flatten the lower 1/4 of the sail.  This opens up the "slot" between the main and headsail and will make your boat more forgiving to steer in overpowered conditions. 

By moving the leads forward, you are adding power to the sail.  For medium air and lumpy conditions, powering up the sail can help give you the extra punch you need to get through extra chop.

Headstay Sag - Getting the proper headstay tension will help you adjust the shape of your headsail.  Less tension equals more sag and a fuller, draft forward sail shape, while more tension results in less headstay sag and a flatter jib entry for higher pointing.  Consult with your sailmaker for guidance.

Proper genoa trim can be very difficult to set up originally, but once set up correctly, should be able to be duplicated easily.  For best results, consult your sailmaker, boat designer, or even your local hot shot for one-design racing class.