...Once you're there, it helps to have a rough idea of what it is you want to do. With Amsterdam (Schipol Airport), they have a currency exchange center located in the center of the airport. It's not the worst exchange rate, and there aren't any hidden fees, but I recommend only getting around 50 euros there before moving to the trains (buy a ticket!) and heading to Centraal Station.
Once there, you're within 5 minutes walk of the infamous Red Light District. I like to either stash my one carry-on (handbag) in one of the luggage lockers, for about 6 hours (costs about 1 euro an hour). That way I can go to my favorite coffeeshop in the heart of the RLD, relax for a while, then leisurely find a cheap hostel to stay in without having the burden of lugging around an additional 30 lbs in dead weight. By the time that you've bought the one ticket you'll need to Centraal Station (~10 euros), enjoyed some beverages (day-old Heineken on tap) and smoke (no, not cigarettes), you're probably getting light on €. Hopefully you've located a suitable hostel to stay at for at least that night.
Hop back to the main boulevard in front of Centraal, where you'll find an ATM near the easyInternet Cafe (owned by the same company as the cheap easyJet - RyanAir's main competitor). Take it easy with the ATM, but when you do withdraw, do it big. I'd recommend multiples of €100, since you'll be slapped with the same terminal fee by your bank and their machine there regardless of how much you pull out. Then, stash it in an interior, zippered pocket. Never, ever put it in your jeans or worse, jacket pocket. There are people out there who do nothing but pickpocket for a living. Amsterdam has virtually no violent crime, but they do have a hell of a lot of pickpocketing.
Grab your bag, get the hostel for €15-20, dump your stuff, and it's off to the RLD again. Since I don't smoke weed at home (in the USA), it's a treat every time I'm there. While the drugs and sex are definitely highlights of the trip, equally important are meeting people and having stories to tell once you get back. Being alone, you can hop from bar to bar to bar - however I've wished at several points before that someone I knew was there to share in the good times. So far, I'm the only one with either the inclination or the necessary finances to travel abroad on a whim. From that point on, it's all you. Try to visit at least a few museums (Amsterdam has somewhere around 40?!), such as the Van Gogh museum or the Richtmuseum - both of these are suitably impressive for telling older people, such as parents, more 'mature' friends, girlfriends) about... you come off as being a cultured gentleman, and not sex-hungry pothead.
You mentioned that wherever you go, it has to have "tons of ~8's". I realize it's cheating, and some people take issue with it, but the Red Lights are filled with girls that easily fit this description. If you asked what a prostitute in Baton Rouge looked like, I'd have to guess when I said old, wrinkled, and probably black (no offense meant). If you asked what one looked like in the Wallens (RLD), I'd be able to tell you it depends on where you are.
There are different sections of the district (actually, there are 3 Red Light Districts in Amsterdam, but the "main" one is the one which caters more to tourists, and thus has the hottest women working). One section is near the old Church, and is to be avoided at all costs. This area is filled with African women. Now, I'm not in the slight bit racist, but these girls are simply horrendous. Many are overweight and virtually all will tap loudly on their windows as you pass by, sticking their heads out and saying "sir, excuse me sir, can i ask you something?". Definitely keep walking. Thankfully, this only encompasses about 2 square blocks total. By and large, the rest of the district (some odd miles if walked in full) is filled with ladies of stark contrast. These are the ones raved about in all of the magazines reviewing the RLD. Eastern-European girls, Dutch girls, Asians; small, big, natural, fake - you name it. Since there's so much money to be made, there are many girls of Playboy (and above) standards, it's easy to see how the unwary tourist can get scammed if he isn't careful. Oh, another word to the wise: If you're there, avoid Bloedstraat. This is the same as the old Church area, except it's filled with transvestites and bondage girls. Scary stuff, and having taken a wrong turn down it once I hurried to the end of the street, greeted by laughter by some people I'd met who knew the area better than I.
Also worth noting are the street people. They aren't many, but they can be very persistant if you give them an opening. Basically, they are emacipated African men who will walk by you saying "Speed, weed, exctasy" so fast you might mistake it for an actual Dutch word. Never deal with these bottom-feeders. If you look at them in the eyes, they might follow you around for a block or so before finally giving up. In the past, I would say "Nyet! Nyet!" (No! No! in Russian). Since I don't know Russian, my accent must have sucked - one screamed "I KNOW YOU'RE AMERICAN!!! as I walked away. I've since found a new trick, and it's one that works very effectively on the persistant ones - meaning those that follow you for over a block. Put quite simply, you bark like a dog. Since these people are usually cracked out (I once saw one pee on his hands, then continue to wash his face with them...only in Amsterdam), the specter of a person barking at them causes them to vanish almost instantly. It's either that or say "Police" several times. I prefer to bark.
Enough with that, if you want more information on the specifics of the RLD, such as rates, recommendations, warnings, and other advice let me know and I'll post them here. Now, it's on to whatever comes to mind next.
Travelling solo is obviously more dangerous than going with someone else. You should set up some sort of schedule with your family or friends letting them know that you'll send out an email every other day or so, along with giving them an itinerary as to where you'll be and when, so that if you happen to fall in a canal and get hypothermia, they'll know to look for you in Amsterdam and not Budapest (another source of 8's, 9's, and 10's). Carry around with you an expired form of ID, I recommend using an old drivers license or going to get a state ID before you leave. Make 2 copies of the main section of your passport, one for your luggage, and one for your pocket. Bring 2 debit cards, one for inside of your luggage and one to carry around. Since these will only work at an ATM, and are useless without your PIN, you don't have to be as careful with them as you would credit cards, but don't lose them either... being alone on a different continent with no way of getting money (well, a wire from your parents perhaps) isn't the best position you want to find yourself in.
Fast forward to the end of the trip. Make sure you get up in time to make it to the airport at least 2 hours before your flight leaves. I can't stress how important this is. Last trip I made, I figured that all flights are generally late, so I could take my time in getting there. A leisurely lunch and farewell smoke with the other students I'd met ensued, and I bought a space cake to eat on the way to the plane. By the time I checked in and ran to the gate, wolfing the space cake down on the way, the plane was already pushing away from the terminal. Thankfully it stopped and a very quick but methodical search was made by customs before I was permitted to board. Almost cost me $500 extra to buy a new ticket back!
Okay, that's all I can think of for now... if you have any other questions just post and I'll get back to them in due time
