What steps should I take in college to land a career as an aerospace engineer?

Do an internship or co-op with an aerospace company. That's the best bet. Also maybe join a few LinkedIn groups dedicated to that industry and participate a little here and there. Meet some aerospace engineers and talk with them about their work. Work experience and networking will help the most to make you competitive. That and, obviously, the skills from your degree program.

You can also do stuff outside of school like making model planes, learning to fly (expensive!), etc, but those are nice-to-haves rather than essentials.

The single most important thing you need to do though are ace all of your classes and pad your resume with leadership positions, instead of just being involved.

Recruiting programs at places like Lockheed Martin and Boeing are hit by tsunamis of resumes. You basically need to be awesome. Vague, I know, but there you are.

The magic number for GPA in Mech/Aero engineering is 3.0. That's the minimum cut-off at most of these companies. Get your GPA to 3.5+, run one or two student societies (preferably industry related like Formula SAE or AIAA, etc) and do all of that early enough that you can, as Pran Mukherjee suggested, land yourself a co-op.

Which also means, if you aren't in college yet, you should factor in whether or not aerospace companies recruit from the school into your college choices. They recruit from most top engineering schools, and also big state schools that do engineering research.