In my opinion, these are questions that can have a list full of answers, but I'll be giving the very generic answers, and if any other member also wants to answer, feel free!
Deities are often seen as spiritual beings of a higher power, which already means working with one can not only give your practices a major boost but also provide you with more protection.
You should work with the one you worship, and overall have a great relationship with. Deities are powerful beings, and only working with them once and never speaking to them again, can be considered rude to that deity. So, it's always best to ask for help with a deity that you have built a relationship with.
You can start by having an altar for the deity, and leave offerings. Offerings do vary depending on the deity, some enjoy flowers. other incenses, liquids, and food, it all just depends on the deity. This is why it's important to do research on that deity to understand what they enjoy and don't enjoy.
In my experience, it does take a while to formally build a bond with the deity, and years for that deity to contact you. This is one of those things where it does not happen over-night, it does take time.
You should work work with the one u re most attracted .I work with several deities.My first one was Maat ,an egiptian godess.She appeared in my dreams several times, i was hearing her name in my head .It was unknown to me so i started to do some reseach to find out who she was.