Assuming you are using leaded solder, 370-400.
Too hot and higher risk of damage though most components are quite tough.
Too cold and have to apply heat for longer so its a balance.
Also consider size of the tip, size of connection and solder gauge.
Very small contact point means less surface area for transfer of heat and if large connection or solder gauge means longer contact time.
It's really something to practice where it doesn't matter until you get a feel for it.
I had all the same questions when I started (left unasked), and no amount of instruction will tell you more than those first few attempts.
Just remember to look for the solder flowing into the joint. If after 5 seconds nothing is melting, either contact is not good or iron too cold.
You shouldn't need hotter than 400.