Hitchhiking is harder than in many other countries, it is possible though with more patience. Many of the drivers that will stop are Chinese (blue car plates). Most people don't know anything about the concept and will just say "no" even if they already told you that they are going into the same direction. Most people outside of touristy areas don't speak English. In the north hitchhiking is much harder than in the South.
The police seems to make it's own rules about camping in Laos. In many areas it is usually no problem and in some cities it is possible to find empty houses/buildings. Some authorities even suggest places to camp.
It is illegal (?) to sleep outside in Laos as the government wants tourists to spend their money on guest houses. Don't overly worry, however -- Zenit was woken up by police once when camping in plain view on the road and only had his passport details taken. On many more occasions nobody bothered him.
The police in Muang Ngoy doesn't accept people to camp and wants them to pay a high fee and acts corruptly.
As in Thailand, also in Laos it is possible to sleep in Wats (temples), but due to government tourism policies it's all much less certain than in Thailand. As in hitchhiking, the further north you get the smaller your chances get to find a place to sleep in a temple.
People are more distant to foreigners than in many other countries and it is not common to get invited into people's houses.
There are few Couchsurfers in Laos, not a major source of free acommodation in Laos either.
Staying in hotel's lobbies is possible in minor cities (rain, too cold, too hot...).
A good way of staying for free is to help hostels/hotels/guesthouses with their online appereance and stay for free in exchange. (Taking pictures, writing reviews, signing them up for websites etc.).
Food is quiet expensive compared to other countries in Southeast Asia (cheapest meal roughly $2). It is possible to be invited from drivers while hitchhiking, since many of the drivers are Chinese and like to show their high hospitality.
Wifi is available in any hostel/guesthouse and in many restaurants.