Torches can hold any amount of weight in sand or gravel on top of them.
With a wall of lava between you and your mine cart it's possible to right click it and get it, going through the lava, without getting hurt!
Looking at any block type and clicking the center button the mouse will automatically switch to that block if it's on your hot bar.
Location, Location, Location
Hit F3 to open the debug menu to see your coordinates of where you are.
Shift-click the output of the crafting table to instantly move it to your inventory!