To make nice leaves Iadd a touch of piping gel to thin icing and a tip #67, #68 or so. Hold your bag at a 45 degree angle. Squeeze kind of hard at first and then ease up as you move the tip. You may need to open the tip a bit by putting a thin knife in your tip and "rocking" it back and forth a little! Hope this helps!
Personally I have found the 349/352 tips to be WAY easier and more consistent in making good leaves. It makes a difference shape than the 67 tip, but I like it better and never have had a problem with it, just using regular consistency icing. However, if you like the 67, go with Missey's advice! 
Personally I find that tip 352 makes beautiful leaves. Very smooth and the tips of the leaves are very pointy. When you start making the leaf - squeeze a good base (let if fan out) and then you can either move in an up and down motion as you draw out or a pulsing motion of in and out as you draw out toward the end of the leaf. If using the 352 tip - it looks like a birds beak with the bottom section of the (beak) lightly touching the surface. I think you'll like the leaves it produces. 
Definately add the piping gel to your frosting and make sure the frosting is a thin consistency for leaves (peaks should flop over when testing consistency). Hope this helps.
There is no hard fast rule for that question but let's say I have about a half of a cup of green, to that I will add about 1/4 teaspoon of piping gel...if I'm not happy with my practice leaf, then I add a little more! Yes..of course...if you add too much it will be runny!
Hi everyone! I've tried the 352 tip and I'm very happy with the results! 
I added piping gel and now my leaves are perfect!
I would greatly encourage everyone to try the 352 tip if you are having
trouble with your leaves.
Thanks again to everyone who helped!
Hershey, how wonderful! It's such a great feeling--and relief!--when we figure out how to make things work. Good going.
Quote by @%username% on %date%
%body%