To take as much advantage of weapon mods as possible, you should try to grab the following perks when you can: Make sure to always grab superglue, since adhesive is necessary for every weapon and armor mod. Scrapping those items will leave you with a fresh set of components to work with. The important thing to remember before you begin modifying and crafting is that you should collect as many items and loot as you can carry, and bring it back to your settlement once you’re ready to start.
Armor is modded separately at its own workbench. To craft weapons, a weapons workbench is necessary. Our scrapping guide, linked above, tracks which crafting components can scrapped from which junk items. To turn weapons and junk into crafting sources, you’ll need to scrap them. You can craft weapon mods from both weapon parts and random wasteland junk.