Your CV is a crucial document in your professional career. You will use it to apply for fellowships, jobs, awards, and funding. Your department may use it for merit/bonus determination. They certainly will for promotion/retention purposes. Especially when starting out, when your CV is short, the temptation to pad it is very strong. Today I am telling you to avoid the temptation and just don't do it!
1. Standing out for the wrong reasons
It is often obvious when someone is trying to pad their CV. People reading your CV don't use the "stair method" to find the longest CV--for whatever evaluation purpose, the point is to look for quality, not quantity. When on a committee where people are evaluating dossiers together, you don't want to the one people read out loud for a laugh because your padding attempt is so obvious (and, unfortunately, this does happen).
2. What is "obvious padding"?
Please DON'T list more than one or maybe two manuscripts in preparation. Anything can be in preparation, and it looks like padding. If you do list anything in preparation, don't bother putting a journal name. It is meaningless until submission. Only list submitted manuscripts that are actually submitted (including a manuscript number is helpful). True story: when I had a phone interview for an industrial position, my interviewer was using the CV I had originally submitted 3-4 months before the interview. I was asked for updates on everything not listed as published, including manuscripts listed as in prep, submitted, and in press. Since I had only listed things that were actually in the state I listed them, I was able to tell my interviewer that my "in preps" were submitted and update on the status of my submitted and in press manuscripts.
Please DON'T list random local talks (group meetings, practice talks, talks required for your program, etc) as presentations. This does not make you look in demand, it makes you look like you think your CV is not impressive enough. Talks will come as you get more experience. DO list poster presentations at conferences--these count. Subbing for a lecture in class belongs in teaching, not presentations. Some people list interview talks. I didn't, but I can see the argument either way.
Too much random stuff obscures the real meat. One CV I saw recently had a peer reviewed publication in a fairly well-known journal buried under a whole bunch of things written for things like the local school paper and random newsletters. Also, time marches on. In my opinion, as you age, you need to remove things from previous stages. If you have a Bachelor's degree, remove everything pre-high school. If you have a PhD, remove everything pre-University. For academics, everything from University on usually stays. For non-academic positions, space is at a premium, since page limits are a thing. Keep details on the most recent, then just list previous experiences with place and date to save space.
3. Keep fluff to a minimum
In the American context, people don't usually put hobbies and family status on CVs. If you do list hobbies, don't lie about them to sound cool (yes, this happens--you don't want to go into an interview listing martial arts as a hobby and then be unable to name one). You do need to be prepared to discuss anything you put on your CV, since interviewers will often pick something that sounds interesting as a conversation starter.