I just recently purchased a 2006 IS350 in blue onyx pearl. I’m planning to do a paint correction to the car but I have a question about a small rust spot. What would I have to do to take it out or what would I do to prevent it from spreading? Here is a picture.

 

Open the driver door, there's a sticker at the bottom of the frame. Look for C/TR, Color/Trim, take a picture of it, go to dealer, buy a touch up paint. There's some instructions on how to use it, prepare the surface, apply the paint, wait 30 min, apply paint, let it dry, apply clear coat etc. You can also YouTube all that stuff. Keep in mind that fresh paint will not look the same as faded 14 year old paint.
Good Luck.