If you are aiming to go trekking in Nepal, Pokhara can be a good base to start your trip as there are plenty of agencies that can help you with planning your trip and lots of shops where you can buy all the gear that you need. It is recommended that you take a guide as you will have a much richer experience and also will be contributing to the local economy in this way. There is no signposting on the trails so it's best to ensure you always walk with someone. There are a number of good maps you can also buy in Kathmandu and Pokhara which show all the possible routes. Do pace yourself as many of the routes are comprised of very steep stone staircases and if you are not that fit take it easy on the first few days.