The kind of stuff I'm expecting: "Python", "contributing to open source projects", "personal projects on GitHub"
Obviously could just say "Loads of experience" but I'm more interested in the low end of the scale - the stuff you'd need to get that first software engineering job or internship and get "on the ladder"
Biggest mistake made by many (including experienced pros) is that they focus on their Resume instead of really trying to understand what the employer wants/needs. If you really have something that the employer is looking for specifically, your chances of at least an interview call goes up.
Honesty: if I can't immediately tell that you are over-stating your experience, I will find out in the phone screen.
Fit: something that helps me think that you'll be a good fit with my team from a personality stand-point. This may be represented by listing hobbies (though be careful with this) and the types of projects you work on.
Attention to detail: Your resume should look like something that's professionally crafted. If it doesn't, I am going to assume your code looks the same way.
Back when I was applying for jobs several years ago, I would tailor my resume for the job that I was applying for. The more your experiences matches the listing, the better. In my case, being somewhat of a generalist, I have some experience developing web, desktop, cli/server and embedded code, so I would rewrite my highlights at each job where appropriate to best address the skills being looked for.
Oh you are a rails developer? Show me your work. This speaks volumes over "3 years of ruby blah blah blah"
my $.02
All entry-level devs have the same kind of resume. Find a way to be an exception, while being relevant to the position.
Always worked for me.