Avensa (along with its offspring, Servivensa) was Venezuela's main domestic airline until it went bankrupt in 1999. It now operates on a reduced scale. Its place has been taken by Aeropostal, which has a network of routes servicing most major domestic destinations. There are half-a-dozen or so smaller carriers including Aserca, Laser and Avior, which service regional areas. The lack of railways means that buses are the primary form of transport through most of Venezuela, and services are generally fast, efficient and comfortable. There are frequent buses from the main Caracas bus terminal to almost every corner of the country, and prices are kept fairly low by the high level of competition.
Driving or motorbiking gives you added flexibility, but it's expensive both to take a car into the country and to rent one while you're there. Additionally, be aware that road rules are rarely observed by local drivers, which could make the undertaking somewhat hazardous. Stops at national-guard and police checkpoints are common, and travelers should follow instructions and be prepared to show papers or be searched.
Local transport includes cheap but crowded bus services and inexpensive shared taxis. Caracas has a modern, efficient and cheap metro.