Since the patch of KSP Ver1.0. The adding of heat and the adjustment of atmospheric calculation make the SSTO flight become harder.
So, the SSTO fighter has to be rebuild and retest to achieve it objective to orbits.
This Shared file of SSTO build by DE has been able to perform the SSTO as the video shown below.
Although the efficiency are not very good. but it is a method to achieve a SSTO Fighter.
basic instruction to reach the orbit.
1. fly with 40~50 degree(depends on the fight pattern) full thruster at reach the maximum height
2. switch to rocket booster to reach the orbits speed when in maximum height.
youtube: http://youtu.be/u00V0YYmtRQ