Interface
For your Interface I would recommend using Weakauras and Bigwigs.
Weakauras will give you the opportunity to import a lot of helpful stuff to keep track of your cooldowns, buffs and debuffs.
BigWigs for having a boss mod helping you out to plan our cooldowns ahead of time and be prepared for certain abilities that are about to happen.
Macros
Here are some useful Hunter macros everyone should have:
Trueshot, Trinket & Berserking Macro
If you have a trinket which cooldown lines up perfectly with Trueshot, you use both at the same time. This just gives an extra action bar slot for anything you want. In case the trinket is out of cd and Trueshot is not, you just press the macro to use the trinket.
/cast trueshot
/use Berserking
/use 13 or 14 ( Trinket slots)
Aspect of the Turtle Cancel Aura
You can cancel Aspect of the Turtle by pressing it a second time but it has a small delay in case you click it too many times in a short period of time. This macro removes that delay so use carefully.
#showtooltip
/cancelaura Aspect of the Turtle
/cast Aspect of the Turtle
Misdirection Mouseover or Focus Macro
Misdirection is an important ability in Dungeons but also in Raids: This macro will cast Misdirection on the target you are currently mousing over. Otherwise, it will cast on your Focus target.
#showtooltip Misdirection
/use[@mouseover,help,nodead][@focus,help,nodead]Misdirection
Party Leader Misdirection Macro
This macro will cast Misdirection on the Party Leader.
#showtooltip
/cast [target=party1] Misdirection
No channeling macros
#showtooltip Aimed Shot
/use [nochanneling:rapid fire] Aimed Shot
/cancelaura Aspect of the turtle
This has to be put in every spell that you might cast after Rapid Fire, like Aimed Shot, Multi-Shot, Arcane Shot and Steady Shot. It prevents you from clipping Rapid Fire. You can then spam these abilities even while channeling Rapid Fire without breaking Rapid Fire that has a longer channel duration than the actual GCD.
Cursor macros for Volley and Steal trap
Volley Cursor Macro
#showtooltip Volley
/cast Salvo
/cast [@cursor] Volley;
Steal trap Cursor Macro
#showtooltip
/cast [@cursor] Steel Trap
Allows you to instantly use Steel Trap or Volley where the cursor is.
Weakauras
Having good WeakAuras can really help you out a lot with keeping track of all the important stuff.
The best thing to do is to find WeakAuras fitting your own interface preferences and play style.
Wago.io has a huge collection for Hunters: https://wago.io/search/type:weakaura%20category:cl3
Legacy of the Windrunners Tracker by Gogey: https://wago.io/hSMVYQvjI
Here you can find my personal WeakAura-Pack which i update regularly: https://wago.io/4QwOwBAhd
If any questions comes up, the Trueshot Lodge is your place. The discord server is by far the biggest hunter community and there are a ton of friendly people helping you out with your questions if you ask nicely.