As someone who's has the game a few weeks more than a lot of you, I've got to say - stick at it. I'm nowhere near being good (I'm currently hovering around a C-) but here's a few thoughts on how I've improved a bit.
Your first week at the game will pretty much suck, I spent mine getting my arse handed to me by laggy Americans. Once you start to get a bit more experience though it's a really good game with a steep learning curve.
A lot of the game is about balance, get an idea of the character's strong points and then exploit them. The Ninja characters are all kind of middle of the road/jack of all trades type who are strong at everything but not the fastest, while the ladies are all pretty fast but not that strong. There's a couple of fast male characters who also aren't powerful (Elliot and Jann Lee). Then there's the characters with strong kicks, or strong grapple moves (Master Chief, Bass).
You need to pick a character who can exploit the weaknesses of your opponent in the beginning as well. The biggest difficulty I had was against the fast characters who do a lot of combo chains (Christie, Kokoro). You can go two ways, either pick a fast character and keep your distance and try and pick them off between combos, or pick a strong character like Bass or Gen Fu and get in close and just hammer them into submission.
The biggest move in DOA4 is probably the launch move - usually an uppercut or a high kick that launches your oppponent into the air and allows you to do a chain of moves unchallenged. Also learn which combos end in a stun, as you can then go straight into another combo. The sparring mode is your friend in DOA4 - every character has a slightly different control scheme and it pays to learn it.
It's also important to retreat and advance - if you just move in close and stay there you will get pummelled by any experienced players. By the same token, don't pull off the same combo repeatedly unless you want to be countered a lot. Try and switch up attacks between high/low/medium and kick. Don't be afraid to stick to one or two fighters and get to know them inside out either.
When it comes to countering, the best thing to do is go into sparring mode and set the CPU to attack with basic combos like KKK or PKK and practice getting the timing of your counter right with every different attack then can throw at you until you can get it most of the time. If you can't counter yet, then blocking is your best form of defence. You can also counter a lot of moves sort of 'unofficially' by getting another attack in first, i.e. a mid punch will usually break up a running attack and a high kick will stop some high attacks.
There's an awful lot to remember in DOA4 even though on the surface there's not much to it. So keep persevering!
As a side note... Alpha 152 is just an annoying *****. The best way to beat her is to stay in close, and link your combos. Low sweeps are effective as are uppercuts. Stay in close and as was said early, keep mashing the kick counter when she attacks.