How can I dodge red shells and blue shells?

Obviously, the easiest way to get rid of a red shell is to shoot an item backwards when driving straight forward. As for dodging them, as well as the blue shells, there is a way. It has something to do with the turn that you can do where there are blue flames behind the vehicule and when you stop turning it gives you a boost. Apparently, if you time it right, you can get enough of a boost to avoid the shell. I've never been able to do it but it's been done before.

Search "Mario Kart Double Dash - Mushroom Cup - 150cc" on youtube. The guy avoids a red shell.

You can't necessarily 'dodge' Red or Green Shells, but you can shoot other Red or Green Shells or drop Bananas to 'block' them from hitting you...

As for Blue Shells, I don't think you can, at least I haven't found a way of successfully doing it everytime yet - if you do, let me know...

On the red shells if you carry like a green shell or bananas you can throw it behind you to stop it and if you don't have anything I found if you hold L or R and releise it before it hits you it sometimes works but not all the time. As for the blue they can't unless you go through a warp. Like on DK mountain or star road.

Hope this helps

To dodge red shells get a small boost with your car by drifting to the side and a small boost will appear when it turns blue let go of the L button and turn quick and it will pass you.For blue shells,when you have a mushroom or something speedy at the last sacond before it hits you use the mushroom and turn it will go straight ahead of you,this works for me sometimes.

Red-Throw Bananas at them when they ar about to hit your car.
Blue-Keep using the Powerslide thing.

Items can block them.

Use the little turbo thingy for red shells, I do it all the time, and for blue shels...hhmmm....take a lot of shortcuts on the tracks, it makes it harder for them to find you then