Also, make sure to read nip-50. Keep in mind that not many relays support nip-50 though. Nostr.band is one of the few relays that I know of that supports it. You can check out my Advanced Nostr Search app to see how I use it. 

https://github.com/nostr-protocol/nips/blob/master/50.md

https://github.com/SamSamskies/advancednostrsearch