There’s nothing quite like sharing a few long moments with a mountain gorilla family: the first glimpse of black as a juvenile jumps off a nearby branch, a toddler clings to its mother’s back and a giant silverback rises to size you up. To make the most of this life-changing experience, planning ahead is essential.

Any time you can. The experience will be incredible no matter when you go, but there are advantages to going at different times of the year.

It’s generally easier to track gorillas in the rainy seasons (March to May and September to November) because they hang out at lower altitudes. You may also get better photos in the rainy season, assuming it isn’t raining at the time you’re with the gorillas, because they love to sunbathe after getting wet. Then again, you’ll need to be wearing some serious wet-weather gear.

The busiest times on the mountains are December to February and July to August. Scoring permits takes more effort during these months, but that won’t matter if a tour company is handling things for you.

Permits are required to visit the gorillas and booking ahead is always a good idea, particularly if you’re planning to visit Uganda’s Bwindi Impenetrable National Park and Rwanda’s Volcanoes National Park from December to February or July to August. If you aren’t travelling in these months and you only have a very small window of opportunity, you should still make a reservation as far in advance as possible to be safe.

To make a phone booking for Rwanda, you need to pay a deposit by bank transfer, while in Uganda you’ll need to provide all the money up front. If you can’t get a gorilla permit on your own, you’ll need to go through a tour operator, which is often a good idea anyway. In the Democratic Republic of the Congo (DRC), you can book online.