First (just like any drugs), you should be sure that you are in a safe/comfortable place. and have a back up just in case it doesn't go the way you think it should. Your set and setting are very important to how well you are going to enjoy any drug's high, and if you don't feel comfortable BEFORE using, there is little chance it will get better AFTER. Let alone, there are times when things change, and this is why I recommend having a simple (safe) backup plan just in case things don't work out the way you want or expect. Any drug can make a great time 10 times more fun, but they can also make a bad time 1000 times worse too, and just a little forethought can make all the difference!
Second, don't burn the meth, you will cause the rest of the bowl to taste TERRIBLE. If you are still new to smoking meth, you may want to smoke smaller bowls until you get used to the heating and rolling, as this will prevent you from wasting a lot of it. As this is a huge pet peeve of mine, I always have two or more clean pipes. This allows everyone to smoke their hits the way they want without bothering me or anyone else. This also makes it nice so if for whatever reason it does get burned, you can switch to a clean one. Best advice to prevent this is be patient when heating it up, don't get the lighter or torch too close, and find a good smooth rolling pattern with your hands.
Third, when taking hot rails, be sure to be careful how hot you get the tooter. Trust me, there is not much that hurts worse than hot liquid meth hitting the inside of your nose, and it can cause some serious burns. You can prevent this by getting a longer tooter (so it can cool more before getting to the nose), but this doesn't work if you are just getting it WAY to hot. I personally heat it up just enough to get the tip of it glowing a light red (using glass), but I stop before it starts to "melt" or bead at the end. If you notice the end your heating is starting to change shape at all, and/or, starting to "round off" (bead or look melted) you are probably getting it hotter than you actually need. Also, if you smell "burning hair", or feel even the slightest discomfort when inhaling, its too hot.