(Hello, I wanted to tell you I love your blog. You're a great Fifth Doctor. But as a roleplayer, I need some advice: how can you be sure you are keeping your character in-character? )
// Wow, thank you, anon!
As to making sure you're keeping your character in-character, I'm assuming you mean for canon characters, and that's what I'll address specifically here.
Everyone's got their own methods. I'm not here to say one way is better than another; it all depends on what gets your brain-gears churning. A lot of people recommend starting with understanding the character's motivations and their inner workings. Personally, I find trying to make the goal understanding the secret of a character's universe a bit much to bite off and chew.
For me, I like to start first of all on watching the character's actions, facial expressions, speech, etc. etc. It applies to book characters too. Have they got a pet expression or a particular motion they do with their hands? The Fifth Doctor, for example, tends to put his hands in his pockets.
Next step is to note when they do it. Fifth Doctor here will put his hands in his pockets if when he's smug or sad.
Once you've studied the character you want to play for a while, and you've got a definite image of the in your mind, congratulations! You can now play them! Of course, you're far from done yet. It takes me weeks to become comfortable playing a character, and months to consider myself good at it. It's a discovery process. Every so often I exclaim "SO THAT'S WHAT HE THINKS WHEN HE DOES THAT!" Every so often I get embarrassed when reading my old threads, and I wonder "Whatever made me think he's actually like that?"
If you love your character, it's definitely a rewarding process. If you don't, I don't know what you're doing. You learn a lot about the individual.
How do you know if you're RPing them in-character? Honey, visual your person. Imagine the sound of their voice. If it's a book character, imagine hard. If it's someone you can get an audio clip of, listen to their voice from time to time. I won't lie... I use that clip of the Fifth's Doctor's voice on my blog every so often. I have songs sung by actors who played some of my characters on some of my other blogs' playlists.
If you can imagine them saying the dialogue you write, and seriously performing the actions you invented, then they are in-character. When you write this character, you are, however, somewhat making them yours. These are adventures they've never experienced, and people they've never met. You have to draw from their past to create their future.
And if you're doing things right, you won't end up with the same person you started with. Because realistically, people learn and grow, and some things they encounter will change them, for better or worse. You'll find happy RPs and RPs that will have your character wanting to cry in a puddle of tears and lost hope.