To get in the mood of being somebody you aren't, it helps if you are dressed for the part. It not only helps you feel the part, it helps others to relate to your character.
Now, with summer coming on we're not expecting Ventrue to wear 3-piece wool suits. However, it's difficult to role-play with a character who is supposed to be a well-heeled Ventrue when the player is dressed in torn shorts and a faded t-shirt.
Make an effort.
A little imagination goes a long way.
Use common sense.
This also applies to equipment that a character carries on her person. Imagine a character saying, "I'm carrying a machine gun, 2 changes of clothing, a laptop computer, and an occult library."