Get the T7-01 droid companion

Crew Trainers can be found both with your faction's fleet and on your faction's capitol city, and possibly on other planets as well.

You can have three professions at a time, but only one of them can be a crafting profession.

Each crafting profession has recommended gathering professions for it. For example, Artificing (to create light saber mods) recommends Archaeology (for crystals) and Treasure Hunting (for gemstones).

Bonus tip: Talk to every trainer before choosing your professions to complete your codex entries for professions.

For the most part, your crew will do the crafting and gathering for you.

Once you have multiple crew mates, it's a good idea to send the ones not with you on crafting or gathering tasks.

During normal questing your conversation choices may affect your companions affection towards you. They must be present in order to gain/loss affection towards you.

Class quest missions that take place on your ship affect all your currently gained companions. These happen anytime it tells you to use the holoterminal or the ships intercom on your ship at the end of a quest.

As a side note, you can always hit escape out of a conversation sequence if you don't like the fact that your companion disliked your choice and choose a different one (but that sort of defeats the purpose of a RPG, besides you can give them gifts later anyway to make it up to them).