Something I always tell to new artists who want to start doing commission:

Advertise yourself!
Do artshares, make a pinned post w/ your commission info, put comms status in ur name!
Make sure ur art is easy to find (in your media tab) if possible!

Get that bread!

It’s also nice to have a place where it’s easy to find previous samples of your work:
moments collection on twitter
archive sites like Insta and tumblr
a portfolio site with a gallery
an online queue list like trello
invoicing is also advised
a terms of service

Kristina has a great thread about making a TOS (terms of service) for your commissions:
https://twitter.com/kristinadraws/status/1231251196968607744?s=21 https://twitter.com/kristinadraws/status/1231251196968607744

Make sure to also read up about royalty fees, commercial and non-commercial licensing as this will affect the price of your commissions.

Read more here: https://www.nolo.com/legal-encyclopedia/licensing-artwork-negotiating-monitoring-royalty-payments-30093.html

Also if your clients don’t come to you, then you have to go find them.
Forum sites like @gaiaonline , @flightrising, @toyhou_se or @reddit have areas where you can do commissions.
There’s also other sites like @fiverr , @DeviantArt and @ArtStationHQ as well. And more probably

Also remember, even if it’s uncomfortable and taxing to do:

Be nice and professional.

You’re selling yourself as much as your art and what you can do!
Clients need to know they can work with you in the long term!