I think you should just be careful and sensible until you get more experience, but here are some general tips:
1) Clean toys thoroughly after use, make sure they're clean before use.
2) Try to be as clean each time as possible yourself as "things" can add friction that could contribute to a tear.
3) Lube yourself first, then lube your toy. And after first partial or complete insertion lube the toy and maybe also yourself again, to make sure the lube is getting deep enough and is also covering all contact surface area.
4) Remember rest days,- just like in bodybuilding, as tissue damage needs time to be adjusted for and healed to avoid actual physical/structural damage. The more intense (aka damaging) the play/workout, the more rest is needed. When i play close to my limit and/or feel a bit soreness afterdays i typically wait about 3 full days if rest before the next session. If i'm in my comfortzone i'll probably play every other day or even every day, but not for an indefinite amount of days succesively. Light play also adds up if you do it every day without ever giving your body the opportunity to maintain itself.
Lastly/5) Go slow, be almost overly cautious and keep reading what other people say but listen to your body and trust it's signals over strangers. Also keep hemorroid/tear-suppositories at hand at all times for precautionary use in case you after play realize you've gone too far. This is such a boring answer, but it's the only one i can think of that'll enable you to keep playing. If you hurt yourself it can be weeks, months or years of rest and possibly being back to square 1 again. So don't try to add centimeters each session or each week even. It's a lot like strenght training/bodybuilding actually, and you're probably going to go a bit too far and get hurt a couple times. The trick is to make sure it won't be too bad. So be careful, take your time, remember that you need rest even thought your body feels fine, and know that experience is going to make you a master.
Now go wreck that muffin