So... I just decided to venture into the mysterious land of online bidding known as eBay. Any tips for bidding, finding good deals, or avoiding bad sellers/counterfeit games?

Your best bet for games is to check the item picture and make sure it is not a stock photo, but is a picture of the actual item on sale. You should also check the feedback of any prospective sellers as this should tell you the kind of experience others have had buying from them.
Also I would avoid buying from buyers listed as Hong Kong etc. as these are often knock-offs. You should also check the sellers other items as this can tell what kind of seller it is i.e. an individual or a store.

Don't buy from anyone with less than 99.0% rating, always look for the lowest price, and in case you're ordering from outside your country, try to make them send it as a gift.

I tend to avoid sellers with any particularly dodgy looking pages but thats just common sense really. Good feedback is obviously a good thing, I tend to read the bad ones and see if their points sound valid or if they're just whiners
Never bid early, note the end time of the auction and set an alarm 5 minutes beforehand so you can jump on and try to win the last second bidding war. Bidding early just drives the price up without any real benefit because there'll be at least one other person who wants what you want. BE SURE TO BE LOGGED IN! I missed an auction for a really cheap laptop because I went to place a bid a few seconds before the end and it asked me to log in...
When it comes to the end of the auction, decide on your maximum afforded price and don't go over it in the enthusiasm. If the current bid is nowhere near that maximum when there's 30 seconds left, put in a last second power-bid for your full amount, that way people who are trying to outbid others by 20c at a time will endlessly get a 'your bid is below the current maximum' or 'you've been outbid' and their bids won't have a chance.
Also, try not to compete with me...
Good advice about hong kong sellers but sometimes the cheap knockoffs do the exact same job as the genuine items, fairly sure my 8gb sdhc isn't a legit sandisk but it's been solid as a rock
Also good advice about the stock photos. Whenever I'm buying games, unless they're actually new, I always ask to see a photo of the disc surface. Not only can you check for scratches but its a good test of the seller's willingness to put in a bit of effort

Question: Buying from a power seller is generally safer, right? Or is my assumption wrong?

One thing I'll guarantee, you will run into trouble at one point; it is Ebay after all.
I sell and buy a fair amount, and I'd say every 10 'transactions' there is always one which I have to tussle with. Be it just late delivery or a full-blown PayPal dispute.
Just don't start selling till you know what you're doing, I went in too soon and almost got burnt.
Don't whatever you do buy computer components, I lost about £50 that way with a fake.

Fake? What was it?
Usually, yeah

Percentage ratings means a lot, but you need to check how many items have been sold & what the complaints are.
Sometimes, new sellers end up with a low rating due to a small number of items sold and one negative. Check the negative person, and see what ratings in general they have given. You do get people causing trouble by giving out negatives for the sake of it, when the deal went through normal.
Also, check the number of negatives given in the past few weeks, months. Any seller can run well, then get into trouble and suddenly, things don't work for them.
Ask for photos, and check the item carefully. Especially with older hardware/software you get items that are similar enough to pass for something, until you try and use it, and find a version number or button is missing due to a model number difference.
Since you're a fellow Australian, I'd also recommend OzTion and The Trading Post, as both focus on this country but deal with bidding/conflicts differently. Though I've not used them in the past 8 months, I had good success finding stuff, though it is harder to find the 99c deals.

If you don't have paypal already get that and use that for buying on ebay, nearly ever other method of payment is asking for trouble.

Hahaha, I already put 11 items on my watch list ^^; And thanks for all the tips and suggestion, guys; I'll probably bid one or two low-value items first, just to feel how the system works...

I hate people who sit around obsessively refreshing auctions, then snipe my leading bid with 4 seconds left to go on the auction.

Thats why I put my maximum bid in at the 15-10 second mark, to counter that

Don't trust chinese knock-offs. Damn things are so temptingly cheap...

I avoid them with games, antiquarian books and collector's items in general. Condition's often better with a private seller. Power seller's rarely actually grade items and when they do, grades are often wrong.
For most everything else, they're generally better.
Expressly avoid buying from Hong Kong, Russia, or foreign countries outside Continental Europe, Canada, the US, Autralia, and the UK.
Use paypal.
Feedback score is mostly useless since they made it damned near impossible to leave negative feedback of late. Read the older comments. It's pretty much impossible for a power seller to have feedback of less than 99% unless they kill people.
I've never had major problems with ebay, and I've bought a lot of stuff off of it. Go for buy-it-now when possible. Snipers (people who bid at the last 10 seconds or so using automated software) are annoying.