There are several things that may help providing the guitar is not broken i.e slipping machine heads, cracked body etc

1) Tinning new strings. This is where you place a small dollop of solder around the string wind that keeps the ball end of the string on. This prevents some stretching

2) Putting a small amount of lube (I use chapstick) on both the nut and the bridge surfaces that come into contact with the string (not too much now !) this can work well with trem systems so may not be so good for an LP

3) Winding on more string at the peghead. B. B. King is quoted as saying this is a very cool way of sating in tune even though I think it looks ugly

4) Monitoring humidity. Atmospheric humidity can cause wood to expand and there's not much you can do about this other than crank the AC. I moved from London to Iowa and the difference in winter time and summer time humidity here amazes me. I don’t know what to do about this other than to use a guitar case humidifier in the winter and keep retuning in the summer