Hi.

It very much depends upon the game and the community, which is true for both muds and online games.
Some muds apparently jump down your throat really majorly for the least ooc comment, others get so into rp as you said you have to actively right a major character.

Two muds that I can highly recommend rp wise are clok and avalon (avalon I'm just trying myself).

Clok has a community heavily based around rp, but many skills to learn and much crafting. While there is a policy about what you can and can't say out of character, nobody will rip your headoff for saying something ooc and people are genuinely very friendly. You don't need a massive background or concept, just choose one of the starting locations to come from in the game and work from there, you actually have to ask in character to find guilds in the game to decide what your character is ultimately goig to do, though the other nice thing about clok is there are lots of activities and such to try out.

Find out more On the clok database page
And of course The Clok website 

Then there is avalon, which I'm playing at the moment.
Avalon has a really unique concept for the game called realplay. This means you don't choose a background or whatever, you just start in on the game asking questions. However the game is setup in such a way as to make it possible for you to become involved in roleplay. Most high officials in the game (including it's literal gods), are actual human players, the same goes for cities and professions, this means you deal with people quite a lot, and have to for example get questss and badges from your guild in order to progress, but your guild are real humans.

There are elections, wars, those who craft and mine, and a lot of other very complex systems, indeed I'm just figuring out the game myself.

Find out more On the avalon website 

Also,  don't be put off by the fact avalon has a payed subscription option. There actually is an rp option called sponsorship where your city or guild will literally give you a free subscription in return for working for them in game, sinse they gain a lot from you just being a member of their organization, so no worries with how much you decide to play whether you want to pay or not.

Ahoy!
@BlakeT, lol that's funny. I've never been able to fall asleep by playing games because I have to do thinking. Reading will usually put me to sleep at night. Anway as dark said clok is a good mud. It's very complex and it has a very friendly community. I used to play a lot it's fun to just hang around sometimes and chop down trees or talk to other characters. Another good one is prometheus: the eternal wars. That one is frustrating and nice at the same time. It's frustrating because you have to give your character a description and you have to make choices on how you want your ships, communicators, and such to look. But it's very fun because there are channels for all kinds of things. Ooc, private, chat, things like that. The people are very friendly, heck I spent a lot of times just talking to a lot of good people lol.
@Dark, well I'll have to check out avalon your post intrigued me. I haven't been on muds lately my laziness is getting in the way I guess lol.

Unless things have changed since the last time I played Promo is not really RP.  I second Dark's suggestion, clok is a good starting point. Then go from there.

Thanks for all your help. I tried Clok. It works for me. I'm no longer in need of a mud to RP in. Just some guts to initiate RP. LOL.