First, in order to know how to effectively make beta bucks, you always need to assess the market situation. Beta is pretty much meant for you to craft your own gear and make your own way through the game and maybe try out the auction house because you have free currency. Currently, the market is flooded with cheap, craftable items and the really good items are very expensive. When taking advantage of the market, the first thing I do is look at the prices of materials. The material prices for subtle essence and common scrap are 1 beta buck each. The only mat worth looking at is the fallen tooth, which goes from about 1.5 beta bucks to about 8 beta bucks. There is one yellow craftable item that can be created, which is the apprentice slingcock (one handed crossbow) for demon hunters. There is an excess of this item as well as some of the trash yellow, which aren't for levels 10 and higher (the level cap is 13). On a last side-note, you also can't search for gear that your character can't use, so in order to be able to search for everything, you need to make a character for every class so that you can search for that certain kind of equipment.
The current crafting situation is that you can't craft items for profit, because the beta is so short people will only pay for the best items around, which in most cases you cannot craft. The only viable yellow item that can be crafted is a one-handed bow (apprentice slingcock). But, the mats are too expensive for it to be worth it (about 50 beta bucks) and each bow sells for about 25 beta bucks on average. Most other items you craft are basically obsolete for endgame beta players. Overall, right now crafting isn't a big beta buck-maker.
There are a couple things you can do to make beta bucks in the Beta. First, you can go through and bid on or buy yellow items below the price of the fallen tooth (or if you can find regular or magic items below 1 beta buck). Alas, you will often be outbid on items, so try to shoot for buyouts instead. Afterwards, convert the equipment back into materials and sell them. Farming is another profitable way to make beta bucks in game, just by either selling the gold or the mats that you receive (and sometimes a really, really good item). This is a great way to make beta bucks if you have time to spare. Also, if you have extra, selling your gold from the auction house is another good way to make some beta bucks.
Obviously, there will be more ways to make money in the real game, as you are restricted to levels 1-13. But, we can observe patterns that happen now that will give us insight into what kind of trends might appear later.
So, knowing what we know from the beta, how can we prepare for the coming of the actual game? Well, knowing what people are going to want to do is a good start.
The fact that there are tons of craftable items on the AH solidifies the fact that people are very dedicated to leveling their professions. Also, people are even crafting items that no one can even use in the beta (even up to level 24!). The only reason that people are even buying gold off the AH is to level their professions. There are basically no other gold sinks right now, as there is not even a gold auction house.
Also, the fact that people are dumping gear for such low prices shows the average player's ability to determine the actual value of items when it is something they don't need. We will be able to take advantage of this, and convert the equipment back into materials for a profit. A quick profit without the problem of The 72-hour re-listing cooldown.
In addition, the fact that most of the mats are selling for 1 beta buck demonstrates the willingness to dump items when they are of no value. You can just ride the wave of cheap materials in this manner to level up your professions.
Although the beta can tell us some things about what the average player will do in the Diablo 3, the beta can tell us only so much. To some degree it will sort of be a guessing game, but I will be working to eliminate this game of chance as much as possible at my site which can be seen by clicking on the reference box below.