Look after your gear and it will look after you.
When packing your kite on coarse sand - pull the kite wingtips together so the kite is folded in half, then roll up the kite with both wingtips together. This prevents sand getting inside the kite, that can work its way into seams and cause wear and tear.
If screws on your board keep working loose, use some medium strength Locktite to secure them.
Kites: Small fabric tears and cuts can be fixed with stick on patches. You might get some supplied with a new kite or you can buy them from kitesurfing shops.
When applying a patch to your kite, first swab the area to patch with alcohol (such as methylated spirits) to clean it. Trim off corners of the patch so they are rounded. Carefully peel of the backing then firmly push on the patch. Apply one a patch on both the inside and the outside of the fabric.
Lines. Lines that become furry over time can be treated with beeswax. Lines with abrasions or nicks should be replaced. A line breaking while on the water is not much fun.
Be careful to keep sand out of your larks-head knots when attaching your lines to the kite. Any sand in the knot will abrade inside the leader loops and reduce their service life.