Satellite tags have been widely used to investigate the biology and ecology of marine species (e.g., migration, vertical movements, reproductive behavior, post-release mortality). The techniques used to tag the animals are substantially different depending on species and the experience of taggers. Tuna have been tagged onboard with manual sticks, spearguns, or harpoons. For billfish, the most common technique is to use a harpoon as these species can be dangerous to handle onboard, are difficult to bring onboard, and are very sensitive with high mortality rates once onboard. Here we present the key elements that can help to maximize the success of tagging from our experience on 84 tags on billfish in the Indian Ocean. We investigate the potential effect of different factors (tagger, handling time, fight time, position of the tag on the animal, …). We show that the position of the tag on the animal is critical for the subsequent retention time of the tag while other factors are less significant. The best position is determined to be below the first dorsal spine and above the lateral line. Retention time was XX times longer when targeting this area compared to other locations.