Master's in mechanical engineering

Hi!

I’m a current first year mechanical engineer and plan to pursue a masters degree in mechanical engineering later on.
I wanted to know whether it is recommended to take a few years off school to work and then return for a masters or it is better to go straight to grad school after undergrad and then look for work.
Note: I do plan to do a few internships during my four undergraduate years to gain experience.

I also wanted to ask what I should be doing during these 4 years so that my application for graduate school can be competitive and I can get into a top school for the same.