We're only halfway through but going ok so far. Things that have helped here -
Having realistic expectations - adolescence isn't easy and it is normal and natural for them to be moody, emotional, tired, grumpy, embarrassed by you etc and for them to pull away from the family and want to spend more time with friends etc. don't set yourself up for disappointment as you can't get through this phase without some of the downs.
Being available - to chat, to give lifts, to return the right form, to lend money etc. I have found that being able to be flexible has really helped us as so often their plans change or they forget stuff etc. My parents worked very hard when I was a teen and so it was other parents that gave me lifts and that meant mine didn't have much idea of what I was up to of who with. I try to be the one that gives the lifts and meets the friends etc.
Being welcoming - I've made sure the DC knows that our home is their home. They're welcome to invite others over and I always have easy to prepare/share food like pizzas, snacks, noodles etc in a cupboard so guests can be accommodated. This means I have an idea of who they're hanging out with and what they're generally up to/into. DC1 had 5 or 6 friends over at the weekend and we went out and left them to it. Came home to find them folding the pizzas boxes into the recycling and plates stacked next to sink!
Keeping them in the real world - we're pretty boundaried about screens and social media. Our DC are pretty busy with clubs/activities/sports and family time, walking the dog etc. this goes back to being available because it is a drain on our time and resources to keep them engaged but it is so beneficial. A lot of the angst and upset that goes on in the friend groups happens on social media platforms they're not on, which saves a lot of stress! I encourage real life meet ups and am happy to give lifts or pay for tickets etc to help that happen.
Engage with school - my DC know that I know who to contact re worries and that I will do it. They know that school and home are in contact and communicate.
Boundaries around behaviour - I let a lot of stuff go but the DC know what my lines are and what I expect to be stuck to. I've seen a few friends with teens give up almost entirely and I don't think that works for anyone.
Honesty - I talk a lot about what I regret re teen years and why. What I found hard and how it got easier. My DC know that they will mess up, struggle etc but they will get through it. As I did!
I really like my teens and their friends! It can be ok!