Relaying a question from my sister who is a natural curly girl. Basically, she's wondering how to get lasting, defined, frizz-free curls without any stiff, starchy styling products.

Being a natural straightie, I could only guess at what to suggest. Leave-in conditioners? Oils? Waxes? A combination of things? I was hoping that some of the curly girls here could offer a bit of insight. What do all of you do?

I have a couple of differnt things that i do.  Depends on the humidity that day and if,that's a BIG if,my hair wants to behave!
I've used aloe vera gel.  The 100% kind.  George's is the one I use.
I've also used alittle of Herbal Essences conditioner after I've gotten out of he shower.  Just put a little in the palm of your hand,(a pea size to start with),rub your hands together and distribute from crown to ends.  Always start with alittle.  It's easier to keep adding than to have put too much!  Then you'd have to jump back into the shower and rinse it out if you put too much. :( >:(
I've also used John Freida's Frizz Ease Strightening cream.  I know, I know, that's sounds weird. The cream gets rid of the frizzies, yet my hair retains some body.
When all else fails, I put my hair in a braid or just bun it!! 

Thank ya, Curlgirl. I'll let her read over your suggestions and see what she thinks. :)

:)

I haven't said anything 'cause I think my styling might be considered stiff or starchy, although that can be scrunched out.
Yesterday I heard that some people are using KY Jelly to tame frizz.  I have to say, I don't have a frizz problem with the styling products I use.
In case she's interested, I recommend DevaCurl AnGel;
http://www.curlmart.com/DevaCurl-AnGEL-p-57.html
followed by Mirror Curls:
http://www.curlmart.com/DevaCurl-MirrorCurls-p-974.html
Scrunching in the Mirror Curls after the AnGEL keeps the curls defined but soft.  The AnGel is supposed to create a cast on the curls until they dry, then you scrunch it out and the curls are soft.

I also really like Kinky Curly Knot Today and Curling Custard:
http://www.curlmart.com/Kinky-Curly-Knot-Today-p-207.html
http://www.curlmart.com/Kinky-Curly-Curling-Custard-p-778.html
And I use the Mirror Curls with this, too because it gives some shine.
Because my curls are Type 2c (wavy) I need more hold and definition than someone with Type 3 or 4.  You can check out the definitions of curl types here:
http://www.naturallycurly.com/hair-types

I also remember a lady at one of my jobs(maybe back in '86) used KY jelly in her hair.