I decided to present some quotations on backgammon to try to help improve your play.
Quotations on the Openings
"The above opening moves which emerged from computer analysis demonstrate that a number of opening moves that were unquestioned for many decades are now considered suboptimal. One example is the move 13/11-13/8 on the roll 5-2. Although not a bad move, the alternative choice preferred by the analyses, 24/22-13/8, is now generally agreed upon to be optimal." Wikipedia
"For instance, the opening move 8/2-6/2 for a roll of 6-4 was in the past greeted with disdain from experts, but turns out to be on average as effective as the usual plays (24/14 and 24/18-13/9)." Wikipedia
"2-1: The slotting play 13/11, 6/5 and the splitting play 24/23, 13/11,
the two most common plays, seem to be about equal. Nothing else is a
serious contender." Kit Woolsey (1995)
"4-1: The splitting play 24/23, 13/9 has come out clearly superior to the
slotting play 13/9, 6/5. Probably the reason is that with the builder on
the 9 point there are so many good pointing numbers next turn anyway that
you don't need the 5 point slotted." Woolsey (1995)
If you are playing a weak player, the weak player will often offer a double even when he is seriously behind in the pip count. In this situation you should accept the double and offer a beaver, which is roughly the equivalent of a redouble in bridge except that bridge has no doubling cube. If he accepts the beaver, this gives you the doubling cube. When you have the doubling cube, this is an advantage because it gives you some control over the game. If you fall behind, you don't double. If you surge farther ahead, you can double. However, if you have a chance of a gammon or a backgammon, your opponet may reject the double to avoid the gammon or the backgammon. Therefore don't double if you are likely to gammon or backgammon your opponent.
The fact that you are playing a weak player doesn't give you an automatic win. The weak player can get lucky rolls and win. Weak players will often double when they shouldn't and some will fail to double when they should. Don't double when you are behind in the pip count unless you have a serious block that is trapping his back men. A 6-point block cannot be traversed by your opponent.