How to make data predictions As a total beginner I am trying to apply some "predictions" on top of a bunch of csv files which contains house transactions for the last 20 years divided per area. What I would like to predict is the trend of the transactions for lets say the next year for a specific area.

What general steps would you follow, to analyse those data and then predict?

I read different articles but what I am looking for it is a sort of "best general practice" for this sort of problem.
Regression will work well if your data set is large, but only for predicting current house prices (say, for example, estimating the value of your house). That's what people generally mean when they talk about predicting house prices from current house sales data.

The question of how house prices will behave in the next year is much, but much more complicated, and would not depend simply on the data you currently have. You would need to involve other information and a much more complex model, which would need to involve things like current level of household debt, inflation rate, economic outlook, etc. Daunting.

Generally, speculative prices follow some stochastic process. They depend on the current value, but diverge more and more the farther you go in the future.