I would suggest taking a small hit. Forkbender is right, 50-100 mics. Roughly 1-2 maybe 3 hits of blotter (if thats how you are taking it). Be with your best freind, but make sure you are both ready and aware that it is going to be an intense journey. If possible, locate yourselves somewhere you have room to explore, I find acid makes me want to go for long walks.
A freind of mine has a huge golf course in his backyard, and I will say, I love exploring this place with acid. Make sure you are somewhere where you can get home safley and relativley quickly if you need to. The comfort of a way-station is not something to underestimate, ecspecially with your first trips.
Forget your phone, forget your watch. Time is not important. Forget time. (my suggestions anyway)
Avoid lots of intensety, ie streets with lots of cars, buisnesses, downtownesque areas. The more alone in the world you and your freind can be, the more fun you will have. Let the world become your playground.
Take this moment to really connect to your best freind, and grow your relationship stronger than it already was. (If possible)
Drink plenty of water, and I suggest a snack like trail mix and nuts just to have around. nuts will help you keep your physical energy up along with your mental energy.
Seriously, its called a trip for a reason. Have the night of and next day off. You will thank yourself. Should you choose to do a day-trip, then make sure you have somewhere you can go that night to rest, relax, and sleep.
I say here that it is time to explore, and play. Do it. Do not be afraid to let yourself be silly. The sillier, the better.
Dont be stupid. Remember that your goal is to take something out of the trip to make yourself a better, smarter, stronger person. Have fun, in a constructive way.
Creativity before Consumption. Always.
Disclaimer: Some here may not agree with these practices for LSD use. But I find that this kind of 'playing' often times leads to the self-realization of the wonderful tools these drugs are. And when you realize that for yourself, it means much more. So really just have fun with your trip man, remember what the playground in gradeschool was like?