Finding accomodation is usually easy if you don't mind spending a lot of money. But most hitchhikers don't have a lot of money, so then there are several other options:
Tent
You can bring your tent and sleeping bag and you'll basically be free to sleep anywhere. Beware that in most countries it's not legal to put up your tent anywhere. It's legal in Scandinavia though.
Your driver
It can happen that your driver offers you a place at his or her house to put up your tent. It can also happen that you get a place offered inside.
Hospitality exchange networks
Hospitality exchange networks require a bit more planning. However, sometimes there are gatherings of tens, or even hundreds of hospitality exchange members. If you go there you'll surely get a place to sleep!
- CouchSurfing, 40000 members, nice website
- Hospitality Club, 95000 members, some problems with censorship