Choosing a trek for yourself to do this season can be tricky.
Well, I think it depends upon a lot of things and I try to put a few factors to help you decide that.
For the first timers.
If it's your first time on planning a trek in mountains, go easy. You can do difficult ones as well, but its step by step process if you really want to get into it. You should plan on going to a trek in the month of May or in September. While, in mountains weather is often unpredictable but during these two months the probability of it being expected is more than other months. Wisely choose an easy trek and the area you want to go. Don't study on all the treks too much, it really can be time consuming. To my knowledge, short treks like Deoriya Tal and Chopta - Tungnath are good one day treks. If you want a camping trek, you can go with Kedarkantha or Pindari Glacier.
For second and so on timers,
If you already have done trekking in the Himalayas then I insist go for a long or a slight offbeat trek. Why? Well, I believe after your first or previous experience, you must have enjoyed it and that's you are up to it again. You want to spend some more time in the trekking. So, plan a trek that has diversity in terms of trails, ranges you see and valleys. Milam Glacier trek, Adi Kailash trek and Namik Glacier trek are good examples of it.
If you and your peers are fit and planning an adventurous trek, You can choose treks like Rupin pass and Roopkund trek. You will feel tremendous joy and challenges during these treks.