Interface
It is important you have a way to track your soul shards as well as your wither/immolate on nameplates.
Plater is good for nameplates and allows lots of customization of nameplate features.
The way I recommend to track soul shards is with Weakauras. There are many generic Destro warlock packs that are available on wago.io that will give you all the info you need to be successful.
Macros
Some useful macros for Destruction Warlocks are curse location macros which cast the spell at the location your cursor is when you press the spell.
Summon Infernal Macro
#showtooltip
/cast [@cursor] Summon Infernal
Shadowfury Macro
#showtooltip
/cast [@cursor] Shadowfury
Cataclysm Cursor Macro
#showtooltip
/cast [@cursor] Cataclysm
Rain of Fire Cursor Macro
#showtooltip
/cast [@cursor] Rain of Fire
Also, some useful macros you can use are mouseover macros.
Havoc Mouseover Macro
#showtooltip Havoc
/cast [mouseover,harm] Havoc; [harm] Havoc
OR
Havoc Focus Macro
#showtooltip Havoc
/cast [target=focus] Havoc
Soulstone Mouseover Macro
#showtooltip
/use [target=mouseover] Soulstone
Spell Lock Focus Macro
#showtooltip
/cast [target=focus] Spell Lock
Curse of Tongues Mouseover Macro
#showtooltip
/cast [target=mouseover] Curse of Tongues
Curse of Exhaustion Mouseover Macro
#showtooltip
/cast [target=mouseover] Curse of Exhaustion
Weakauras
Many generic warlock packs are available and all do basically the same thing, it will come down to personal preference on which pack you want or if you want a pack at all.
Wago WeakAuras: https://wago.io/the-war-within-weakauras/classes/warlock