If it's the first time you will use, vaporizing over aluminum foil is the best way because it's much safer than the other routes and you will feel the effects very fast. As long as you don't mix it with other depressants like benzodiazepines or alcohol, it's pretty hard to overdose.
If I were you, I would definitely not shoot it because, usually, once you shoot it, using it any other way will feel like waste (amount and intoxication wise). Intrarectal is another very efficient way to use. Don't get careless or cocky thinking that you can control your use and do it a couple times a week. The amount of people who can use Heroin casually without getting dependent is miniscule.
Finally, try to make sure that you don't have Fentanyl tainted Heroin which can be fatal especially if you don't have a big habit (even if you do, it could be fatal).
Good luck.