Pick your sloes preferably from a sunny site late October,so they are nice and ripe. Buy a bottle of cheap gin, and empty half of the gin into a clean bottle. I add only a little sugar but also add a few drops of Almond essence. you now have two bottles half full! Top up each with pricked sloes (this is the tedious bit-suggest some appropriate music-you can't watch TV without pricking your fingers) seal up and turn each day for a month. They should be ready by Christmas. Last year mine had a lot of fruit pulp, so the previous suggestion about filtering is probably sensible so as to prevent corruption.
Good luck.