DOes anyone have any techniques or something to prevent tension creeping into their shoulder or pre routine to prevent tension at all

thank you
play very slowly in as relaxed posture as possible and only gradually increase speed, note how and where the tension is coming from and correct your technique - dont try and force speed as youll just end with unnecessary tension
Before you play, relax your muscles a bit. Roll your shoulders 5 times in one direction, then 5 times in the opposite direction. When they start to tense up, take a 10 - 15 minute break, then do that again. That should help keep em loose
John Petrucci has a vid where he shows some warm up exercises. When you start playing Guitar, your body isn't used to that extra weight and arm/shoulder positions, so warming up beforehand (even if you've been playing for years) will help.

One exercise he shows that really helps is using your thumb just under your collar bones near the shoulder, and then massaging with a circular motion. Hell, I do that even if I'm not going to play Guitar just because it feels so good. It also helps to do that in areas around the collar bone, it gets blood flowing well.

Once you start warming up at least somewhat regularly, you'll be able to play for longer (or almost indefinitely) without pain. Check out this video for those warm ups, they all really help. You'll have to go about 3 minutes in to see them, there's a lot of bull in the beginning. Check out his other videos if you want also.
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You should get yourself doing some Military pressing. Lifting weights directly up and forward a tad. Works out the shoulders, neck, arms, wrists, and your back. After doing many of those in my lifetime, I have never noticed any cramping from my guitar strap ever. and i have a BC Rich Warlock Bronze. some people tell me that it is a heavy guitar, I beg to differ.
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Good posture: sit/stand straight, don't anchor your wrist. Forcing speed can cause unwanted tension. The Priciples of Correct Practice on Guitar explains this kind of thing better
Make sure you don't hunch over your guitar as most players do to see the fret board... This will hurt your chest and shoulders.

Or maybe you're cool like me and have scoliosis.