Trekking

Darjeeling - Sandakphu / Phalut Trek:-

The best months to trek in this region are April, May, October and November. There may be occasional showers during April and May but, in away, this is the best time to go as many shrubs are in flower, particularly the rhododendrons. There may be occasional rains during the first half of October if the monsoon is prolonged. November is generally dry, and visibility is excellent during the first half of December, though it's usually cold by then. After the middle of December there are occasional snowfalls.  
You don't need to bring much with you on  this trek as there's accommodation along the way. Most places have quilts but in the high season it might be worth bringing your own sleeping bag (you can rent them in Darjeeling) in case there's not enough bedding to go round. Also, since you sill be passing through valley bottoms as low as 300m and over mountain ridges as high as 4000m, you'll need clothing for a wide range of temperatures. Take rain gear whatever time of year you go, as weather can be unpredictable. Acute Mountain Sickness (AMS) can occur at high altitudes.

Although you can get basic meals along the way, everyone recommends bringing along some snacks like nuts, biscuits, raisins and chocolate. You'll need a water bottle even a plastic mineral water bottle will do as there are some stretches where there's no water or places to eat.  
Guides and porters are not necessary but can be arranged through the youth hostel or the trekking agencies.

Before leaving Darjeeling you're advised to browse through the Darjeeling Youth Hostel's book in which trekkers write their comments about the routes.

    This trek to the Himalayan viewpoint at Phalut (3600m) is the most popular trek in the area. It involves a short bus trip from Darjeeling to Manaybhanjang, from where you walk steadily towards the mountains via Sandakphu. Here you can turn back or continue to Phalut and walk down to Rimbik for a bus to Darjeeling. The trek can be done in the opposite direction but you will spend more time walking with your back to the mountains.

Short Cut :-

If you don't have time for a six day trek, you can go just as far as Sandakphu where there are also good views. Sandakphu is actually slightly higher than Phalut, although further back from the mountains. From here you can backtrack to Bikhay Bhanjang and cut straight across to Rimbik in five to six hours for a bus to Darjeeling. Bear in mind that there's no water or food on this stretch.

Darjeeling/Gangtok-Pemayangtse-Yoksam-Dzongri (3939 m):-

6 days exhilarating trek (2B) with exclusive views of the brilliant Dzongri sunset over Kanchenjunga (Higher grade extension (3C) to Goechala overlooking the inner basin of the main range).