I know many people have said this before, but I have still seen quite a lot of people make their resumes more than a page long. Do not do this. I don't really even care if you have ten or more years of experience, I have never seen a resume that needed to be more than a page long. Your resume is not the place to describe yourself (that is what a cover letter is for), and making it more than a page long shows that you do not know how to prioritize what is important to say. Your resume should highlight your important skills, some relevant projects, and some relevant past work. Any more than that, and you will lose your reader, who will be your first obstacle in getting a job or internship.
You are not a Master
One of the best things that you can do, is have a list of skills on your resume. This is a great way to say, for example, what programming languages you know and use, or what APIs you have used before. Listing out your skill levels with them is even better. But please, do not put that you have mastered any of them. I don't care if you have used the language for twenty-five years, and were the original creator of the language, there is going to be at least one question that you do not know the answer to for that language, and when you say that you are the master, you need to be the best of the best.
Imagine how bad you will look if you go into a job interview claiming to have mastery over java, and then they ask you a question that you do not know the answer to relating to java. For example: Do you know what the java keyword Transient is used for? If not, then you do not have mastery of Java, and if you do know the answer, I'm sure there are other questions that will stump you. Do yourself a favor, and just don't use the word "master" on your resume. Stick to words such as "knowledge of", "advanced knowledge", and "intermediate knowledge" instead. These can be especially useful for showing what languages you have used before, and what languages you may have just read about in school.
Don't Advertise for Unwanted Jobs
This is something a bit more obscure, but I think a lot of people forget this when they make their resumes: Don't put down a skill you don't want to use. As an example, I've recently begun messing with ThreeJS, a WebGL library. I will never list that on my resume, mainly because I do not want to be hired to work with it specifically all the time. If a company asks, I can say I know it, but I don't want a ton of companies contacting me to use that specifically. Don't list a skill that you would dislike using at work. I know a lot of people list HTML as a skill on their resume, but my recommendation is to think about whether you would want to write web pages all day before you put that down. Obviously, you can't pick and choose everything (you need to know things like java, and be willing to use them at work), but don't set yourself up for a job you will dislike.
I hope that at least a few people find these tips useful when creating their resumes. While this is geared towards a more technical resume, these tips may apply to other fields as well! As always, any comments and feedback about your opinions on these tips can be left below!