If you're after some guides [@Lady Amalthea] might have some good information for you. She has worked on several guides that deal with GMing and RPing roleplays, as well as linking other articles by members.
Source: [url=https://www.roleplayerguild.com/topics/162563-articles-and-guides-index/ooc][Link][/url]

I would probably suggest RPing 101 and maybe glance through some of the others.

If you are new to roleplay I would generally sticking to Casual. They tend to have lighter expectations on length and detail (although some people can expect a bit more, so choose wisely). From there work on your presentation, grammar, spelling, and creativity. When you feel that you are comfortable with half a dozen parragraphs of detailed IC work, start to look at advance.

Advance is generally for longer scenes with an emphasis on depth, explination, and structure. It will discuss what the character feels with all of their senses, the design on the environment that the roleplay is taking place in, and a length that may take some time to write and for you to sit down and spend time to read.

1x1 is a bit different as you probably have more emphasis on playing GM like. You need to work with your partner to create the world, rather than a group one where you can have someone else do that for you. If you do post an interest check mention that you're new to roleplaying and maybe you wanna try a short, quick-shot roleplay. There's a few people that can only commit to a month or so due to school and work so having a holiday time roleplay might work out for them too.