Don't head your Resume "Resume" or "CV" or "Curriculum Vitae"
Put your name at the top.
Trust me, the person hiring know's its a CV, they've seen a lot.
POD to researching the company / organisation you are applying to. It shows interst and helpd you avoid making silly mistakes.
I was one of the interviewers for a post recently.
One applicant (who had stated on their CV that they considered attention to detail and research skills to be among their strengths) told us that they were particularly interested in gaining experience in Area X of our field. We don't do any work at all in Area X, a fact which is very obvious if you were to Google us and read the list of Areas of Work which is shown on our home page.
The same candidate, when asked if they had any questions for us, asked a question which again, was very basic information about our organisation which is on our website. (the website comes up as the top hits if you google our name, or the name of the person who the application had to be sent to, and the website address is on the footer of our e-mails (the interview details were confirmed by e-mail)
Listen to what the interviewer(s) say
If you are asked a question, answer the question you were asked, not a slightly different question you thought you might get asked (and if you feel you must provide information which isn't actually an answer to the question, own it, say what you're doing - show you actually paid attention to what you were asked.
Also, listen to what the interviewers say even when they are not asking you a question. I have had candidates ask questions which were answered in the introduction we gave them when at the start of the interview.
I know it is nerve-wracking to be interviewed but this makes it look as if you weren't paying attention.
Get someone else to proof read your resume and cover letter
Spell check is a useful tool. So is proof reading your own documents, but consider getting someone else to check it too, as it can be easy to overlook errors, especially in something you have written yourself.
Tailor your application to the job you are applying for
We recently interviewed people for a post as receptionist. One applicant had previous experience both a as a receptionist, and as a secretary, but didn't mention either job in their cover letter, which was all about their most recent job, which was a production line job. None of the skills which the applicant listed themself as having, from that job, were remotely relevant to the job they were actually applying for.
I'm not sure whether this is a universal one, but I'd also recommend that you type all cover letters unless the ad specifically stipulates than a hand written cover letter is required.