Stretching 
Also something that helps prevent muscle aches is orangejuice (drink that after work out). A hot shower in the morning helps you to get going when muscles ache too much (also against stiffness).
Important notes for Stretching:
Warm up first.
Stretching muscles when they're cold increases your risk of pulled muscles. Warm up by walking while gently pumping your arms, or do a favorite exercise at low intensity for five minutes.
Hold each stretch for at least 30 seconds.
It takes time to lengthen tissues safely. Hold your stretches for at least 30 seconds — and up to 60 seconds for a really tight muscle or problem area. That can seem like a long time, so wear a watch or keep an eye on the clock to make sure you're holding your stretches long enough. For most of your muscle groups, if you hold the stretches for at least 30 seconds, you'll need to do each stretch only once.
Don't bounce.
Bouncing as you stretch can cause small tears (microtears) in the muscle, which leave scar tissue as the muscle heals. The scar tissue tightens the muscle even further, making you even less flexible — and more prone to pain.
Focus on a pain-free stretch.
If you feel pain as you stretch, you've gone too far. Back off to the point where you don't feel any pain, then hold the stretch.
Relax and breathe freely.
Don't hold your breath while you're stretching.
Stretch both sides.
Make sure your joint range of motion is as equal as possible on each side of your body.
Stretch before and after.
Light stretching after your warm-up followed by a more thorough stretching regimen after your workout is your best bet.
In addition to stretching major muscle groups, stretch muscles and joints that you routinely use at work or play. Sport-specific stretching prepares your muscles for a particular sport or activity. For example, if you frequently play tennis or golf, working in a few extra shoulder stretches loosens the muscles around your shoulder joint, making it feel less tight and more ready for action.
Source:
http://www.mayoclinic.com/health/stretching/HQ01447
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