I tend to follow certain rules I've made for myself regarding Mass Effect games:
1. Veteran and below are for ******.
2. Always pick soldier on first play-through as the other classes require a depth of understanding that you do not yet posses. Learn the mechanics first before rushing headlong into the deep end.
3. Stick with the ME2 class/weapon conventions - they work the best.
4. Biotics (classes) always look cooler and feel more natural with women.
5. For everything else there's men.
6. Krogans make the best squadmembers. The fun you can have with a krogan tank is unreal.
7. Adepts & Engineers don't need weapons so head straight to gold with them. You can play around with guns later when you have something worth a damn.
8. As soon as you've maxed out your gold/rare weapons and you have at least 5 medi-gel slots - it's time for plat from here on out.
9. Don't miss weekend challenges. And if you have multiple systems do them on both. Trust me this will save you hours of grinding if you game on more than one system.
10. More often than not If it's not 66653 or 66660 you are doing it wrong.