Pakse to Bolaven Plateau

If your questions are that basic you might want to get a guide book and read up a bit first.

There are two routes going in and around the Bolavens, destinations along those routes are being served by public buses out of Pakse.
One is going to Salavan and many get off at Tad Lo.
The other one is going to Attapeu and possible stops are Sekong or Pakxong.
The two routes connect via a road in the eastern parts of the Bolavan Plateau at Thateng and this connection can be used to make a 'loop' out of it.

Of course you can rent a scooter as well and drive on your own.
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I'd suggest that you try to hire a bicycle or motorbike. The towns aren't anything to write home about, and it's the places along the way, with their waterfalls etc, that is the main reason you will want to do this loop.

if you don't want to take a motorbike, i took a public bus to tad lo because i was traveling alone and didn't want to be out riding by myself. it's a hot sweltery ride but doable. cheap, 30,000kip. and 15k kip for a tuk tuk to the southern bus station.
another option is to go to green discovery for a day trek to a couple of waterfalls and the coffee plantation. i had a blast doing it on a one day trek. they said it was easy, but holy shit, it was a little tough going in parts. still it was gratifying to finish and go swimming after.

i stayed at alyssa guesthouse right next to the bolaven cafe (excellent cafe latte and breakfasts). it was super clean and comfortable with wifi in your room as well as computers for the internet. great place. central.
i stayed at the lankham hotel one night and although the room was fine, it was a bit crap in the lobby and the wifi was really bad. some rooms without windows are awful. my friend said hers was dirty.
mine was fine though.
highly recommend was the nang noi questhouse but i don't remember the address.

you could also try the ziplining adventure. i hear it rocks!