Start by taking an inventory of your bike's components and their weights. A spreadsheet helps for this. Also, think about the components that you might not like due to their function. Start by replacing heavy components that don't function as well as you'd like them to.
Rotating weight should be looked at first since trimming weight there will give you the best performance gains. Tires are a fairly cheap way to lighten up your bike by a half-pound. Take a hard look at your wheelset's weight and think about replacing it too.
I don't know the weight of your fork, but it doesn't appear to be light. A nice fork will be lighter and perform better.
Those are the two area's I'd look at first. For everything else, just replace it with lighter, better components as they brake or fail to perform as you'd like them too. (nice brakes are a nice buy if you don't like your MX2's)