Wow, isn't everyone friendly this evening.
Unless you are very small or have low threshold for alcohol tolerance, 2 10mg diazepam is a nice way to start off drinking. Definitely a bad idea to do it the other way around. . . you don't want to be popping pills after you're smashed. The benzo *will* intensify the effects of the alcohol, of course, but You have control over how many drinks you want to add to the batch. 20mg and 2 drinks will get you feeling pretty nice. Another 6 drinks and you'll certainly going to want to watch out for the floor moving around.
Of course, there are so many variables. Maybe you mentioned this but your body weight, gender, benzo and alcohol experience all influence the way you should go about this. Honestly, unless it is Roche or a Damn Good generic, 10mg of valium doesn't do a whole lot. However, since you posted the question, it's probably safe to assume that you don't have any notable benzo experience. I have an enormous tolerance at this point (80mg generic diazepam taken a few hours ago--the stuff is long lasting), but I am thinking of about a year ago, when I still had relatively lovely low tolerance. A 130lb woman (that was me) pops 20 mg (generic, but not bad) before heading out to the bar, with all intentions of only staying awhile, maybe having 2 drinks before I go to meet my friend at 8. I didn't "feel" the valium but it sure made killing time at the bar a lot easier, because it was easier to talk. This, in turn, led to me having several drinks bought for me, lets say 4 more on top of the 2 intended. Now, this was probably on an empty stomach. The time flew by, I went to the bathroom and returned to find a fresh drink. But it was already 8. I had to leave and I knew my body was not up for processing any more alcohol at that point. So I unfortunately had to turn down that drink and hit the pavement.
Now, I am not in an way a model of self-restraint. One of the major reasons I needed to go to my friend's place was because Ineeded to bang phenobarbitol (for horrendous Effexor headaches. But I *did* keep pretty good track of time and I *did* turn down a shot on the way out because I was coherent enough to realize that I couldn't take anymore booze.
Of course, once at my friend's place, having banged the phenobarbitol (which I was using daily, so it was nothing out of the ordinary) I did let my eyes close a woke at like 5 mintues to 10 hearing him mention softly "Didn't you say you had to be somewhere at 10?" Oh yeah. . . about 15 blocks up the street. I got up, apologized for coming over to pass out, and headed out.
You'll want to do this without the phenobarbitol aspect, but the moral is that yes, you can take a small (aka "reccommended") dose of a benzo and have a couple of drinks. Just take the pill(s) first because , IMHO, alcohol makes you lose your senses faster and more completely. The valium, I suspect, reigns in the misbehaving devil who keeps telling you that you're not really drunk.
I think the idea of trying 15 mg with a beer or 3 is good way to start. There's no reason to blow all your pills at once, and diazepam on its own is not a very exciting drug. (Except Roche! I'm sorry, I've just over the past couple of months had my hands on the real thing a few times and it really is remarkable.)
Another side bar, for your next go, is that many people do NOT find valium to be much of a sleep aide. Valium has *never* knocked me out. The primary medical usage is for panic/anxiety and muscle relaxation. Thats not to say that is not prescribed for sleep, nor that it won't work for sleep on some people, but it belongs the anxiolytic branch of benzodiazepenes, not the sedative-hypnotic one.