How can I get a bunch of 1-UPs in New Super Mario Bros(DS)?

I need to rack up a bunch of free lives in New Super Mario Bros (Nintendo DS). What is the fastest technique to get a bunch of 1ups / free lives? (Will the staircase + koopa trick work in NSMB? Where's the best staircase for this?)

Solution 1:

It's been a while, but I liked playing the first level over and over. It has a Mega Mushroom in it. What you do is let the mushroom out, but don't get it immediately - let it scroll right until it almost falls into a pit. Then pick it up and run like crazy to the right. You'll get a bunch of 1-Ups, including when you smash through the ending flag.

Repeat!