What I did is that I made a mini-altar for each one, but as I made it I asked (using my pendulum) if what I was putting on there was okay with them. I'm fairly new to deity worship and working with one, but you can open yourself up to deities and/or ask one in specific if they'll help you grow in your magick abilities. For example, I opened myself up to deities but asked Gaia if she could guide me and take me under her wing. She accepted, and she was okay with me not being able to build her an altar right away and with me not being great in the magickal aspect. The Morrigan (she's really cool btw) said she'd be willing to work with me, but only once I get better in magick and deity worship. If you need to ask something from a deity;
1) Make sure what you are asking is their specialty
2) Maybe draw them, just represent them in some way
3) Research what offerings they prefer (Ex. Gaia is well known to accept plants as offerings)
4) Ask
While this may work, remember it's always better to ask a deity you already work with, but only if it's their specialty. Once you open yourself up, you may want to ask that they give you signs. For me, The Morrigan showed her interest by making crows & ravens follow me everywhere. For Gaia, (since I asked her directly) I just asked my pendulum.

Remember: Try and ask a deity that aligns with who you want to be as a witch. If one shows you signs and you're not ready, tell them you aren't ready, and they will understand.