Most times when learning a foreign language, we get two words at the same time even though the meanings are opposites. Such as left and right, or front and back, or yesterday and tomorrow. However, this is very ineffective. Why? First off, you know you have just learned the two words. And you can easily tell from context that the word is one of the two. But, you must stop and think about which one is which.Usually when this is forced upon me, I try to make some little connection as to which one is which. Take for example, the characters for left and right, 左 and 右. Even by just looking at these two characters you can see a resemblence. So every time, stop and think. What did I come up with to remember which one was which? Well, I imagine being on a road. For 左, if you are driving on the street that starts from the center and bottom of the character, going North, you need to make a left turn to get to the highway. For 右, going North again, but on the street which is the left side of the box, you can make a right turn and then keep making right turns forever.
In order to avoid the word pair problems that I just mentioned, it would be best to learn just one of the words first. Use that word for two weeks or so. Then introduce the other word. Now what you have is a situation where one of the words is very familiar and the other one is not. You now can distinguish the familiar word easily because you've had it for a period of time, while the other word is still 'new,' so therefor it must be the other meaning. With this approach, you don't need to slow down and think about which is which and what is what. You just say, "Ah! New word, new meaning. Old word, old meaning" and that's that.