There's nothing more annoying than going for a run or being out during an errand with your favorite pair of earphones, and having to constantly fiddle with them so they stay put. In my experience, specific types of earbud covers are needed to prevent earbuds from popping out. Here are some easy ways to making them stay put from a DIY perspective...
1. Modding Old Earbud Parts
I've gone through my fair share of earphones, many which eventually broke, leaving a small supply of spare parts. Most important are the earbud adapters for the ears. They won't be compatible with every kind of earbud, but they will offer additional options for the best fit. We actually used an old adapter from some Shure earphones to mod our Apple earphones by simply cutting away the center piece and slipping it over the Apple earbud. The resulting Franken-earphones pop out a lot less.
2. Sugru Tweak
Sugru is an easy to use silicone that takes about 24 hours at room temperature to fully cure. It remains malleable for 30 minutes after opening, offering plenty of time to mod your earphones to your specific ear shape...a cheaper option to custom earbuds (here's another $7.50 DIY kit).
3. The Tie-Wrap Hack
This hack is simple to complete because all it requires is a pair of tie-wraps. While they might not look sexy, they'll get the job done in a pinch. An alternate option is to try and salvage some parts from an over-the-ear headphone model.
4. The Glasses/Sunglasses Option
If you run with glasses or sunglasses, try looping your earphone cord around the end of your spectacles. I've tried this myself and the best way of accomplishing the most secure fit is to use the part of your glasses arms that is right in front of the beginning of your ear. You can also loop the cord around your ear for maximum stability.