1. As with any item of clothing, quality comes first. Never skimp on price if quality depends on it. The best bet is to go for reputed brands like Domke, The Vested Interest, or CampCo.
2. Choose a photo vest that is cotton or cotton blended material, as cotton can breathe and absorb sweat, which makes you feel comfortable. Also, meshed shoulders or backs improve air circulation and are hence preferable.
3. Try out the photo vest before you buy it. While trying out, do take your camera and a couple of lenses along and put them in the pocket to see how it feels. Concentrate especially on the load bearing areas, i.e., the shoulders and the seams. Extra shoulder padding and strong seams are a must.
4. Check out placement and size of the pockets. It should be sufficient for all your gear plus a little more.
5. Look for lining or waterproofing in the pockets. This will be a saviour in case you’re caught in a downpour.
6. Try to buy a camera vest that is light coloured rather than dark, as they absorb less heat and are cooler to wear.