If sharp, lengthen string by adjusting the saddle back. If flat, shorten string by moving the saddle forward. Remember guitars are tempered instruments, retune, play and make further adjustments as needed. There are a couple of additional things that you can do to optimize your tuning stability that have more to do with playing and tuning habits. Each time that you go to play your guitar, before you do your final tuning, play for a few minutes to allow the strings to warm-up.
Metal expands when warm and contracts when cool.
After you have played a few riffs, and bent a few notes, you can then do your final tuning. Remember that with most tuning keys it's desirable to tune up to pitch. Finally, wipe strings, neck, and bridge with a lint free cloth after playing. When transporting or storing your guitar, even for short periods, avoid leaving it anyplace you wouldn't feel comfortable yourself.