Marine Speed Tricks:
I will list each trick and which is the faster method etc.
1) Wiggle Walking: Wiggling your mouse right to left while you walk in rapid succession with no real pattern to it will speed you up. This however is by far the slowest 'trick' available and should only be used if you do not want to jump at that moment. The advantage of this is you still go somewhat faster while making less noise then other methods.
2) Jump Walking: Jump walking is a semi-bhop. Instead of just walking forward or wiggle walking you can jump walk. Ie: Jump and then wait till you regain normal speed and then jump again. Overall this is faster then normal walking and wiggle walking but it makes alot of noise. It also makes you somewhat more vulnerable when you hit the ground because of the anti-bhop that is coded in. Thus you need to use it carefully.
3) Angle Jumping: Angle jumping is a BHOP for marines. Marines are still able to bhop if their second or even third/fourth jump is quickly executed before the anti-bhop code takes effect. This is plausible when you are jumping on something higher then when you started. For instance you can angle jump off a railing or a ramp that is going up. Ramps are special cases because they are continuouly going up and therefore you can bhop up the entire thing if you do it correctly. This is faster then wiggle walking and jump walking and there is really no disadvantage other then the noise you create.
4) Wall Strafing: Wall strafing is when there are straight walls that you are able to use to your advantage. For instance, if your going to topographical from MS you can normal walk forward and use your strafe keys against the railing. If you look to your right while using your left strafe against the railing while also hitting forward you will go much faster then normal. This is better then all previous methods if its a long wall, if its just a short railing I suggest an angle hop and then some wiggle/jump walking after.
These are the tricks that people use as marines to go faster then normal. They take some time to get used to them and after awhile they become 2nd nature.
Marine Jumping Backward Tactics:
Well there is really no trick to jumping backwards more then once but I will explain how I do it and hopefully it will help to some degree. When I jump backwards I actually look were I'm jumping, jump and then look back for an instance. I keep doing this until I need to fire upon enemies behind me. So, In essence I'm not actually jumping backwards, I'm actually Jump Walking while looking backwards every time I'm in the air. Hince how if you have mastered marine movement tricks you can easily incorporate jump walking into a good backward jump style.
Marine Knifing Tactics:
Obviously getting a sense of knifing range is a plus when you are faced with hand to hand, and some people find ducking to be of some benefit. The real trick with this is just tracking, make sure you have the opposition is in your hit zone and try to hit/backup. When I say backup that doesnt mean you should take him off your hit zone or stop your attack if he ever gets back in range again. It just seems that skulks and other things attack faster then marines so it would be beneficial to exchange one hit at a time.
Hope I answered your questions.