I did a penis enlargement routine a few years ago. It wasn't a complicated one, just a warmup, stretching for a few minutes, jelqing for a few minutes, then a warm-down, about 20 minutes in total, combined with pc exercises throughout the day for stronger erections and better orgasm control. 2 days on, one day break. I did it for about 2-3 months before I fell out of the routine. I gained about a half an inch in length and a quarter of an inch in girth. I know it's not exactly the miracle 3 inch gains some of the penis exercise sites promote, but it was better than nothing considering I was smaller than average when I began, and I'm sure I gained more if I kept going (which is why I recently started the routine again). I had no difficulties, except for some burst capillaries a few times, but I've heard that's nothing to worry about, and indeed the red spots from the burst capillaries faded after a short while. I've heard some say that jelqing makes your penis veinier, but it didn't happen to me.
-Make sure you do the warm-up and warm-down. They help to prevent injury, and the warm-up makes the routine easier, increasing blood flow which helps when jelqing, and loosening the ligaments you need to stretch which helps prevent pain when stretching.
- I found it was easiest to do the routine in the bathtub, as you can easily soak your crotch in warm water for the warm-up and warm-down, and you can use body wash as lube for jelqing assuming your brand doesn't irritate your urethra.
-Don't orgasm within a few hours before or after your exercise routine, it slows gains and negates your workout.
-If you feel any pain greater than mild discomfort during your routine, you should discontinue immediately and take a break from your routine for a few days. If you notice anything about your penis that worries you, don't hesitate to tell your doctor, better to be safe than sorry.
-Many of the websites have more complicated routines you can do once you're used to a beginner routine, though I never had the free time to try any of them as they take a good amount of time.