TIP #1
Stay on the same level of drunkness.
If he gets really shitfaced, and you feel comfortable about it, get shitfaced. All that he will be able to remember is that he had an awesome time with you and that he was glad that he wasn't the only one running into walls.
If he decides to stay sober, maybe you should consider to as well. Therefore, he will have someone else to hangout with that can actually hold a conversation with. And you guys can make fun of everyone together!
If he gets buzzed, go for that level. This is the best one, because you are drunk enough to have a great time, but still remember it! Not to mention good things to talk about in future conversations.
TIP#2
Try not to throw up. I know that we can't all control it, but if at all possible, try not to because well its NOT attractive... At all. I'm sure that if it was a good party, enough people would have already thrown up anyways!
TIP#3
Try to stay up all night, preferably just the two of you. Go and watch TV together, or just talk about random shit, cook food! Do stuff that you would do if you were bored. You guys will make so many memories that just the two of you will have.
TIP#4