I try not to use it. Because it is the same thing with saying that "I am in coming" instead of "I am coming" in English.

Eww.. "makta" is really gross

                    Nehir göle akmaktadır. ´The river flows into the lake.´

Is this the best way to express this general fact? Are there other ways?

There is no such thing as "Yarın kursa gidiyorum" in proper Turkish language. "Yarın kursa gideceğim" will be in order...

HAZIRLIYORUM & HAZIRLAMAKTAYIM are not identical in proper Turkish. Any one notice the difference ?

I understand hazırlamaktayım as being in the state of preparing something. Like when my suitcase is open on the living room sofa for days and I am filling it by little by little preparing for a journey while actually not concentrating on this job. It is just somewhere in the bottom of my mind all the time while I am doing other things.

I see there are situations when it is important to make this difference. What I cannot understand is why -MEKTE structure is used for expressing general truths while the generalizing -DIR exists and you can attach it to almost anything. That is why I asked.

Correct. one is continious, the other is intermittent.