Here are various videos showing nicely the forehand and backhand technique

Forehand

Chinese champion Ma Long discusses his forehand drive technique followed by commentary of a Chinese coach.  This is a very long video demonstrating many techniques broken down into chapters.  Just view this part several times to get his main points.

Another forehand drive tutorial by coach Yang Yang which gives a more precise points.

Coach EmRatThich pointers for developing good forehand drive.

Forehand drive stroke taken apart into its most basic elements by English & Irish champion Jason S. – here

Forehand shown by an Australian Pro William Henzel in very slow motion with comments and common mistakes pointed out. Very instructional.  Forehand counter hit & block. However, his technique relies on accelerating by whipping the wrist more than body rotation.  He also advises against opening the racket (more force) too much and for closing the racket (friction).

Video of various forehand techniques taught at the Chinese table tennis school made by a group of visiting French junior players.  One thing to note is the relax-squeeze technique used to speed up shots and recovery to ready position shown starting here.

Forehand loop against underspin (slow spinny forehand loop)

Attacking the underspin for shake-hand grip (fast forehand loop)

Attacking the underspin for pen-holder grip (fast forehand loop another)

they note that the ball contact timing is early falling.

Forehand topspin by Zhang J.K.

Backhand

Another backhand drive stroke video – here.

Backhand attacking with footwork

Backhand counter hit and block

Backhand topspin against underspin

Fast backhand topspin against underspin by Vietnamese coach

Backhand block against topspin

Backhand Banana Flick

Seiya Kishikiwa backhand

Backhand block

Article about active backhand blocking and its advantage over passive blocking.

Backhand block shown by Ping Skills’ Alois Rosario

Backhand block shown by Russian coach

Active backhand block shown by Canadian player Jean-Luc Hinse

Backhand and forehand block shown by Japanese female player, including common mistakes. Controlling block just with a racket angle (more open for less spinny loops, more closed for loops with more spin). Instead it is better to keep the angle more constant and drive the ball with small movement right after the bounce).  She says to press down not up like other literature.  But perhaps this movement is first little bit down then up – in the shape of U or the valley.

Dealing with slow spiny topspin

1. Start with hand position high, so that you can press down the ball
2. Use your waist and put your body weight on top of the ball
3. Contact the ball at the top of the bounce, on the side of the ball and press downward and forward. See training forehand here and backhand here.

Here is a tutorial with drills to practice blocking form Mr. Seth Pech.  One of the unique tips he gives is how to block sidespin loops from left-handed players by going with their spin.