Some of these depend on the person / situation but here goes.
- Music or some other way to drown out ambient noise, invest in headphones, you'll be wearing them a lot and maybe for extended periods and they need to be comfy
- Make sure you know your tools (IDE, Debuggers, etc) and are comfortable with them. It helps a bunch when you at least know what you're doing there.
- Techniques that let you manage your own time (Pomodoro for example) are great in making sure you don't burn out on an issue or solutions you're trying to tackle.
- Always keep in mind that people smarter then yourself have gotten stuck on easier things then you're currently on. ;)
- When in doubt, ask other people, discuss, talk.
- Make sure you have a good chair / desk, I prefer to have the option to switch between standing / sitting for example.
- Get away from your desk, walk, stretch, get sunshine.
- Make sure you have a good keyboard.
- Try to let go of your mouse as much as possible it might be personal preference or your IDE that lets you use it a bunch but trust me, after 10+ years of working as a Full time Developer you WILL feel pains in your wrists eventually.
- Exercise outside of work.. when you're sitting for extended periods of time or even alternating between sitting you're still doing something we humans are not meant to do.
- Make sure you are hydrated.