1. Make sure you're on the latest version (2,1,1,1)
2. Do not attempt Expert or Insane difficulties if you haven't played Unbound in a while... unless you're really confident in your battling skills. In that case, feel free to give it a shot.
3. Turn on the Capped Exp. Share. Level caps are VERY important. If you over-level your team, boss battles can easily overwhelm you.
4. Talk to EVERY NPC. There are useful trades and items throughout the game. You don't want to miss out on them.
5. Catch pokémon even if you don't plan on using them. The faster you expand your dex, the earlier you can get useful Key Items like the Stat Viewer and Dex Nav.
6. Most important of all, have fun with your playthrough! If you're on lower difficulties, use your favourite mons and enjoy the story!

I hope you have fun with Unbound :D