Fastest Way to Increase Spin

Almost everyone wants more spin!

If I were to estimate, among all those whom I have worked with, about 80% wanted more spin. 

About 15% asked for comfort as top priority since they had some sort of pain in their arms.

Only a few (<5%) asked for more power or more control.

What these spin-obsessed folks did not realise, was how paramount power was to generating spin.

Let me make this statement boldly:
To achieve more spin, you have to obtain more power first!

The very nature of hitting topspin is inefficient. Compared to a flat shot, topspin robs power. 

And in many low to intermediate players' quest for more spin, they end up swiping the racket almost 60-70 degrees upwards. That further reduces the amount of forward drive they put into the ball.

Sometimes they get a lot of spin, but it is a sitter. It does not kick forward.

A simple visit to the physics classroom to understand the resultant force under "Vectors" easily explains why. (link)

If you search youtube videos of Federer or Nadal, or any other pro player, you will see their follow through is only about 30 degrees upwards. That's all they need to achieve their 3000+ rpm on their forehands.

If you observe carefully, their shots usually land near the service line and then kicks all the way to the baseline. Average net clearance was only about 60cm or so.

So how should amateurs and wannabes like us hit topspin?

Simply:
- keep the net clearance low (max 60 cm)
- smack the ball hard with a shallow 30 degrees follow through

Of course many other factors play a part, including:
- string type,
- string tension,
- racket flex,
- racket hoop size,
- racket string pattern,
- type of balls,
- court surface,
- swing timing, 
- footwork, etc

From my observations and experiments, power is the most critical and most neglected factor.

Specifically, swingweight.

When matched with the player's strength and abilities, this single variable has the most direct and strongest correlation with how much offensive kicking topspin he can generate.

All other spin factors have a poor correlation.