I love Diablo 3's shared stash and I'm sure you do too, unless you're some kind of weirdo who doesn't like nice things :) Hey, but even then, it's who you are, I'm not gonna judge.
The problem with the shared stash, at least at the beginning, is that it doesn't have a lot of space.
The stash has 3 tabs and only the first tab is enabled when you start the game on a fresh account. Each tab has 10 rows x 7 slots = 70 slots, for a total of 210 slots (for all 3 tabs). The first 2 rows in the first tab are free but from there on you will have to pay gold to unlock additional slots/tabs.
Each 14 slots (2 rows x 7 slots) costs 10,000 gold. To unlock the second tab you'll have to pay 100K. The third tab costs 200K. The second and third tabs come with the first 2 rows free, meaning that you will have to pay an additional 40K (4 double-rows x 10K) to fully unlock each tab.
The total to unlock the full 210 slots in your stash is 100K + 200K + 40K x 3 = 420K.
That's a lot of gold! In the beta I haven't focused on unlocking the additional tabs, though I will if I have time to earn the required gold. But in the full game no one will have that amount of gold from the beginning. Furthermore, it will be a much better idea to sell all your gold during the first few days/weeks instead of spending it on personal comforts. So what to do?
I'll tell you what I'm gonna do. I won't even buy a single 14-slot "slice". Eventually, I will expand my entire storage, but not right away. Here's why.
In the full game my priority will be to level a "main" class to 60, and I already decided on the Demon Hunter. I won't focus on any other class until then. However, I do want to level all classes to 60 eventually. That means that I can safely create all the classes at level 1 and "park" them until I need to play them. These will be my mules. Whenver I need storage space, I will transfer stuff from my main to the stash and then to the mule. Each additional character will provide 60 extra slots.
In addition, I will have 5 character slots remaining. I can easily create dummy level 1 characters for these slots, which will give me an extra 5 virtual storage "tabs".
The total storage for those 9 additional characters is 9 x 60 = 540 slots, which is a lot more than what the fully upgraded stash can offer me.
So all of this space will be absolutely free and I can be certain that it's more than I will need for the next couple of months. The best use for my gold won't be from expanding the stash early on. Stash costs are fixed and won't change (barring a patch), while gold prices will be on the decline from day 1.
The only disadvantage to this strategy? There's a certain amount of juggling involved with swapping items between characters. But that's a small price to pay for how much gold you are saving, gold that you could sell for real money instead.