There are several good ways to get Stockholm:

Train:
Swedish train service

Bus:
Y Bus
Berlin Linien Bus

Plane:
Scandinavian Airlines
Air Berlin
Norwegian Air

And once in Stockholm you can get to Umeå by:

The fastest way, air:
Malmö Aviation
Norwegian
Scandinavian Airlines

The flight from Stockholm to Umeå lasts about 55 minutes. From the airport in Umeå you can take the bus to City Centre, a single ticket costs 30 SEK. Takes about ten minutes.

It's often more expensive to buy tickets for fridays and weekends, so it´s cheaper to come on a week day and leave on a week day.

Most environmentally friendly way, train:
Night train Veolia Transport
Day train + bus Swedish train service

It's the same when it comes to trains- often more expensive to buy tickets for fridays and weekends, and cheaper to come on a week day and leave on a week day.

Taking the night train from Stockholm to Umeå takes about 10-11 hours. You can also take the daytime bullet train from Stockholm to Sundsvall and take the bus from there. This trips takes about 8 hours.

The cheapest way, bus:
Y Bus

Traveling by bus to Umeå from Stockholm takes you about 9 hours.

Regardless of how you travel- most companies offer some sort of Student Discount!

Car:
Info by local Tourist Information Office

Ferry:
Info by local Tourist Information Office