Got to play quite a bit with an actual pro gamer this last week. I even took time out of work (how silly). Sadly, I'm not sure he will be back to this game- he liked it but there were quite a few things he didn't like (understandably).
But here are a few less known tips that he taught me that I thought I'd share..

1. Always keep the crosshairs at head level- You may feel like you can see better with the weapon slightly pointed down however aces rule in any fps.
TIP: practice keeping your crosshair at head level at all times. higher angle close quarters, lower in open areas

2. Walk don't run around unknown corners.
TIP: If your an ads player, sight it before rounding.

3. Two parts of accuracy- Oh dear his accuracy was amazing. Not kidding, ~50% dsg and almost 40% with the Grendel. He didn't pull that trigger until he was on target no matter what. I killed him twice WITHOUT HIM EVEN FIRING A SHOT. I don't advise this play unless you are as good at aim as he is, because a little luck never hurt right??
Good aim is about lining up the crosshairs and pulling the trigger at the right moment. Any one can point at the target, but misses come from pulling the trigger when you're not on target.
TIP: Practice firing/stopping/reacquiring/firing, this will train you to connect the two parts of accuracy.

4. Stop and crouch (ads mid/long range)- I have always been a strafer, and I know its saved me many of times. However if your aim is good enough, a headshot will save you more than trying to make the other guy miss. Since all weapons have less spread while crouching, it makes it easier to get the correct reg for the ace.
Tip: Practice stopping on a dime and crouching the whole time keeping your crosshair on target.

These tips are helping me, and hopefully maybe you as well.

But lastly I want to mention the 'other half' of playing like a Pro..
Pro doesn't just mean to be paid for what you do, it also requires a level of 'professionalism'. Pro teams don't endorse player hating or trolling of any kind. In fact most forbid it. Playing like a Pro requires giving back and being respectful to the players and games that got you there. So anyone that plays this way is certainly not a Pro no matter how good they may be.

Go play and have fun!

Just saying these are actually tips that seem more from a pro Counter Strike player.
Though yes, these tips are very helpful for those that want to get better.
The crouching thing helps but it's not as useful in this game as it's more fast paced and since you have a steriod nanosuit you're an even easier target. :>
The last description I do agree. Although it should be on scrimmages and tournies, on public you can't do much because there's that votekick initiation, op loadout things so meh...