I would suggest India Hikes. I recently trekked with them and I guess they are quite good at what they do. they provide excellent foods, good camps, dry toilets and keep a constant check on your health while trekking.
Try Decathalon , India Hikes, bmcadventures. BMC have part time trekking organizers over weekend which provide you some plan to start working. But individually you need to be fit and a good trekker to work with any trekking company.