The absolute highlight of my trip to Sumatra was Kerinci.
Take a bus/flight to Padang.
We stayed at the Maranatha Homestay, which is not as expensive as it looks like. They also offer a bed in a dormitory for very little money. The place is run by a very nice and helpful Chinese family. http://maranathahomestay.blogspot.co.at/
Then take a bus to Kersik Tua - Kayu Aro (6 hours?). I suggest you stay at the Homestay Binardus Darmin. It is basic but clean. The family are very nice too and the food is delicious. http://i30.photobucket.com/albums/c338/Treibgutspool/Malaynesia/Sumatra_Kersik_Tua/0373-Kersik_Tua_Darmin_Homestay.jpg
The area is fantastic - tea plantations and the majestic cone of Kerinci. My daugter took this photo right in front of the homestay:http://images.summitpost.org/original/664947.jpg
Climbing the summit is a 2-day trek. To the trailhead it is 5km by ojek. Then it is 6.5 hours to the high camp at about 3300 m, and another 1.5 hours to the top early the next morning. Make sure to be at the summit at 05.30.
Dinner at the high camp : )http://images.summitpost.org/original/664936.jpg
Our guide was Endatno Een. I really recommend him. Everything was firstname.lastname@example.org
Endatno offers rain forest hikes too.
Get your guide to show you a specimen of Bunga Bangkai (Amorphophallus titanum): http://kerincinationalparkguide.blogspot.com