Ballistic stretching
Dynamic stretching
Active stretching
Passive (relaxed) stretching
Static stretching
Isometric stretching
PNF stretching
The rule of thumb is to hold each stretch for 30 seconds. It's ok to build up to that.
Relax into the stretch. You might find it more intuitive to tense, but that is counterproductive.
Are you unusually flexible? Many people are hypermobile and don't know it. Look up the Beighton Scale online. If you are, it might also mean you get unusually tight. Stretch every day, both sides, but take special care not to hyper-extend your joints.
Essential everyday functional flexibility exercises:
1) Roll your shoulders and stretch your rear shoulder muscles by holding one straight arm across your body and supporting the stretch with the other arm.
2) Hamstring stretches – lie down and pull each leg at a time, gently straightened with your foot gently flexed, towards your upper torso.
3) Calf stretch – lean into a wall with one leg stretched straight out behind you. Then switch sides.
4) Chin tuck – move your chin straight out from your neck into a "head forward" position (don't move your shoulders), then move it back in all the way so your head is "stacked" directly over your body. If you're used to sitting in a head forward position, you might feel a twinge when your head moves into place, so move slowly. Hold on the stacked position for 5 seconds and release.
5) Kegels – tighten and release your pelvic floor muscles for 10 seconds, ten times. This isn't really a stretch, but it's essential nonetheless and easy to combine with stretches.
6) Cat Cow – On all fours, arch your back and look up for 5 seconds (cow), then reverse and look down for 5 seconds (cat).
7) 20-20-20 Your eyes need "stretching", too! When doing screen work, every 20 minutes, look at something 20 feet away for 20 seconds. This is a minimum! Then blink. Developers have learned this the hard way, and they have made apps to nudge you.
Hold stretches until you feel a slight release into the Stretch. If it takes more than 30 seconds. Back off a little the next time.
I walk a lot and have an impaired ankle so leg stretches are particularly important.
Standing hamstring stretch
Lunging hip flexor stretch with back leg elevated.
Standing quad stretch.
Sitting glute stretch.
Standing side stretches.
I have some back posture stretches that I learned from a trainer but I don't know what they are called.