Before Starting! If there is anything specific you need to know, please ask! I would recommend that you wash and iron your fabrics to make sure it won't fade, fray, shrink or stretch.
Embroidery Stitching: If you have used embroidery stitching, you can make sure the stitches are even by stretching as follows. Lay several layers of blotting paper on a wooden surface and wet thoroughly. Lay the patch face upwards on the paper and, starting at the centre-top, secure along the top with drawing pins. Then pull the bottom down and pin bottom edge, keeping patch taut. Do the other two edges in the same way, smoothing out any wrinkles. Leave till dry, preferably overnight.
Once Finished You can wash the patch again if you wish. This is for your own sake as I'll be washing all patches myself anyway - I cannot risk one poorly prepared piece ruining everyone else's hard work! Add a seam to minimise fraying. Pin a piece of paper with your name and address on to the back. Please check your handiwork.
Links There are also a lot of good sites out there that can give you a place to start. Here are some of them:
Beginners' Quilting Tips is highly recommended for outright beginners.
Beginners corner has a good glossary and introduction to applique.
Beginners' Silk-Ribbon Embroidery teaches ten easy stitches
5 Minute Cross-Stitch
Embroidery Basics
Fabric Paint (A list of links)