Tip #1-You can't be anyone's friend. The moment you do, you will be burned. This doesn't mean you can't be friendly but you can't do any favors and have to treat all equally.
Tip#2-The ETLs will push you around since you are below them in title ranking. This is hard on you when your title falls below them yet your metrics are based on how well their teams do. You will need to be firm with ETLs but know they will see you as a TL and not as an ETL. Ask for your STL support ahead of time and let him/her know you need it from day 1.
Tip#3-Manage your time well. Employee issues can take 40+ hours but you only have 40 hours. Learn how to divide your time between hearing employee concerns and your required tasks of hiring, succession planning, etc.
Tip#4- Whatever you do, observe first, then execute. This could apply to all the ETLs/STLs, etc that I have seen come and go.
Tip #5-A personal tip- Don't stay in your office 24/7. Most people here will state it is because you need to be accessible so employees can know you...for me, I am telling you because I have seen my share of HRs put on a ton of weight. Sitting at a desk, looking at metrics and problem solving issues while drinking a latte is not good for you. Just a FYI.