What to italicize?

I've been having a bit of a dilemma while editing/rewriting: in my first draft, I overused italics for emphasis, as I always do. Fortunately, I find this rather easy to edit out. However, it's a bit confused and inconsistent as far as italics go for the following:

1. Names of computer games. What if it's a computer game a character made themself, not in any way official? I don't think I actually mention any games that exist in the real world (except generic kind of things like "Speed Racer" that may or may not). Should all computer games be/not be in italics or is it different depending on whether or not they exist in "real life"?

1a. One thing I have noticed is that I have a tendency to put stuff I've made up in italics (invented shops, games etc) but real ones not.

2. Shop names. I'm fairly sure big chains like Target, K-Mart don't need italics, but I'm uncertain about smaller independent/small chain stores I've made up. This is quite inconsistent throughout also.

3. Website names. Mostly I refer to websites as suchandsuch.com, without www. or italics. If I were to say the specific name of a website, such as Google, would that need italics like a book title? Talking about the Internet in books is so confusing.

4. Toys/gadgets. Especially in the case of specific ones I've made up for the story. Do the names of these (which would, if the story were in real life, no doubt be trademarked by the company) need italics? For that matter, do the names of the made-up companies?

That seems to be all the questions for now, though no doubt I'll think up more as I edit/revise. Thanks!

1. You don't need to put videogame titles in italics, although it wouldn't hurt to do so. Although, be consistent: it doesn't matter if it's a real game or not, you'd use italics regardless.

1a. As above, whether or not something is real shouldn't make any difference. If you're using italics for made up stuff, you should use italics for real stuff as well.

2. I don't think you really need to put italics for any shop titles, but again, it probably wouldn't hurt to do so. And as before, be consistent: it doesn't matter if the shop is big or small or real or made up, if you use italics for one, use italics for all.

3. I don't think you really need to put website names in italics. As before though, it probably wouldn't hurt.

4. Doesn't need italics, although, again, you could probably use it if you wanted too. And as always, be consistent, don't change the rules if something is made up.

If you're gonna use italics for a particular thing (videogames, for example) then puts all those things in italics, even if you made them up. Whether they're real or not shouldn't matter, because in the story they are all real.

I barely use italics and no-one has ever pulled me up on it. I use them in essays and sometimes in thought and dialogue but other than that, not really. It's a personal preference, but it pays to be consistent.

Echoing the sentiments of everyone else here, be consistent. There, that's italics for you!

Strictly speaking, when quoting titles (of TV shows, films, books, articles etc.) you should either italicise them or put them in quotation marks; NEVER just leave them capitalised. You can even underline them if you want. In informal speech, however, people tend to miss these things out for convenience's sake (lazy buggers, I know, me included). Examples:

"Law & Order."
Slaughterhouse-Five.
Charlie and the Chocolate Factory.

All other proper nouns (brand names, cities, countries etc.) should be capitalised only:
Oxford.
McDonalds.
Hasbro.