Hi, I had a surgery for pilonidal sonus second time, 15 days back. The wound is nice and clean because of daily dressing. What should I do to avoid its reccurence?

Clean and Dry. A complete resection of the pilonidal sinus should result in a cure from this problem. Keep your healing wound clean and dry. If you have hair in the area, then once you are completely healed, you can use a depilatory cream to remove all hair from the area.
Shaving Hair. The only thing we know that possibly can prevent a recurrence is hair shaving. You want to keep the area around the surgery completely clear of hair. Options include regular shaving, laser hair removal or nair (or similary products).
Excision. Typically recommend keeping area clean, and minimizing hair growth- using depilatory agent like nair works. For multiply recurrent abscesses, usually recommend excision of that whole area when inflammation has died down, and attempt closure with a local flap such as karydakis flap.
Keep area clean. You may want to be evaluated for hair removal therapies to decrease risk of recurrence.