So, everyone knows the risks of injecting, but as others have said, safe and STERILE are the way to go. I get gear that readily dissolves in water, have never had to heat it, and just filter it through a TIGHTLY balled up q-tip "bud", though a micron filter is a worthy investment and highly advised if this is something you REALLY want to get into. Have lots of rubbing alcohol to sanitize the area where you're injecting, and once you've pulled out and dark blood starts to pool up, use a dry cotton ball to soak up the blood droplet. After that, just rinse the site with a cotton ball that's damp with alcohol or a prep pad. Best not to use the alcohol until bleeding has subsided due to the risk of blood thinning, and if you're on blood-thinning medication like Coumadin (as I am), that's a MAJOR deal. Rotate injection sites as well, track marks in the crook of your arm will definitely be noticeable if all you ever hit is the brachial vein in the arm and good luck explaining those to your family, employer, etc...ROTATE!
I also want to say that I read so many people who say "Don't start down that road", "Never IV", "You'll end up dead", etc. Everyone's level of "addiction" is different, but I use 3 to 4 nights a week and when you take the time, as you have, to seek out information and to be informed about the action you might take, you're already on a path towards those things PROBABLY not happening. The dangers of IV are not the drug itself (unless you're copping bad gear, but powder is fine most of the time), but complications from poor hygiene, missed shots, sharing needles, and vein damage if injected without letting the vein have a chance to recover. As shown above, the "vacuum" method of registering is the best way to know you're in the right place for maximum effect and minimal damage. Don't "hunt" for a vein with the needle halfway in your arm if you fail to register - pull it out straight and try again. Some people will develop a needle fixation where the rush from the gear is so great they think any ground up pill or powder is safe - this is NOT the case. I'm in Georgia, all I get is white powder/chunks that develop a tan-ish tint when dropped into water. Probably comes from Philly or Baltimore. It's been consistently good for the last 4 years, point being that it's the type of gear ready-to-go, minimal but ESSENTIAL prep necessary. Ground up pills are NOT meant for IV, which is why it's a pain to turn them into something that is injectable.
Sorry, long-winded but wanted to throw my 2 cents in there...IV'ing won't destroy your life unless you let it. If you get the feeling you should stop, by all means PLEASE go back to insufflation or just take a break, even if with other opiates if you've already got a habit. Just don't get a needle fixation - that's the most dangerous thing you can do. Abscesses are not fun and not really easy to explain to people you know.