What are the typical steps to be admitted to a masters program later in life? I graduated from college with a BS in Civil Engineering a bit more than 10 years ago. My GPA was about 3.0, but I think that was pulled up more by some electives and liberals arts classes that I excelled in because I recall struggling a bit with some of the more advanced technical courses and walking away with an A+ in History of Rock and Roll I and II.

Since graduating, I've since tested for and passed the PE exam and am licensed to practice engineering in addition, I've since become a lot more proficient at advanced technical aspects of engineering via practice.

I've never before attempted an application to grad school, but more and more I'm finding professionally that there are a lot of advantages to having a broader knowledge in engineering than the narrow specialization that my BS prepared me with.

What are the typical steps I would need to complete in order to gain admission to grad school. Is it necessary to take the GRE? Would a GPA below 3.0 in technical courses pretty much bar me out?
Each university will have its own requirements for all these things, so the place to get answers is with them. They might be different at every place. I don't think the age of your degree will matter too much if you've been working in the field and learning things. 

But your application letter should stress your experience, not just your academic credentials. It might be good to mention the sophisticated sorts of things you've worked on. It will always be good to mention what you hope to get out of a new degree. 

If you did poorly in major subjects, however, you may have to account for that - not so much why you did poorly, but how that hasn't affected your capabilities since you graduated. I suspect that you will have an interview unless the new university is especially large. Be prepared to speak honestly about your background and goals.