How do I save a table to Data Store?

You can use the http service. The script may has some error:

local table = {a = "0",b = "0"} -- The main table
local ds = game:GetService("DataStoreService") -- datastore service
local hs = game.HttpService -- the http service
local nds = ds:GetDataStore("test")
local value = hs:JSONDecode(nds)
if value == nil then -- if it the first time you start the game then you start with the main table
    value = table
else
    value.a = value.a + 1 --we want to add 1 to a every time
    value.b = value.b + 2 --we want to add 2 to b every time
end
local encode = hs:JSONEncode(value)
hs:SetAsync("test",encode) -- may be it (encode,"test")

You would save it as you would another type of data, but do remember the 65536 character limitation and that it saves the table encoded in JSON, to get the length of the encoded table length, doprint(string.length(game:GetService('HttpService'):JSONEncode(table)))

Example:

game:GetService('DataStoreService'):GetDataStore('AName'):SetAsync('table',{'a','b','c'})
local t = game:GetService('DataStoreService'):GetDataStore('AName'):GetAsync('table')

http://www.roblox.com/Forum/ShowPost.aspx?PostID=128157478 < That should help you.