Step one - Make a straight up line of 4 blocks

Step two - On the third block place a ladder

Step three - On the fourth block place a block, with blocks around it, with a minetrack on it, and a minecart on top of that

Step four - Break the block above the ladder

Step five - The minecart should of fallen down onto the ladder, the blocks around it will keep it in place

Step six - You can continue doing this until you are at the desired height

Step seven - To use the elevator, go to the bottom, look up, and enter the minecarts. To go down, jump through the minecarts, the ladders will prevent you from taking fall damage.