How do I choose the order in which my blockers are chosen?

Under normal circumstances, an attacker can be blocked by multiple blockers. However, I have not been able to find an explicit way to choose which blocker I can pick to be the cannon fodder. For example, when I block a 3/4 creature with a 2/2 and a 3/2 creature, logic dictates that I should choose to block with the 2/2 first, so that my 3/2 would survive; the game quite often disagrees by picking the stronger of the two to block first. Is there a definite way to make this happen?

No, there shouldn't be a way to choose which creature will block first. There is however a possibility to choose a blocking creature to attack first(so if you attack with a 3/4 creature and enemy blocks with 2/2 and 3/2 creatures, YOU can choose which creature to attack first).

To enable choosing creatures, you have to enable it in the settings. Go to Help & Options -> Settings -> Advanced, and uncheck the Order Blockers Automatically option.

Source: MTGDotP 2012 and 2013 (I don't think that it changed)

According to the rules (from Innistrad upwards), the way the damage is assigned is as follows:

The owner of the attacking creature chooses the order of blocking creatures which the attacking creature will deal damage to. So if the attacking player has a 10/10 and the defender has one 5/10 and five 5/1 and blocks with all of them (ignore that it's a stupid idea to block like this), the attacker can decide to who he will deal damage - logically, he would choose the five 5/1 creatures and the last 5/10 would just soak up the last 5 points.

Similarly, if a blocking creature would be blocking more than one attacker, the owner of the blocking creature decides the order of the creatures it's blocking in which they are dealt damage by the blocking creature.

So, the short answer comes to No, it would be against the rules.