I just recently made my first scarf.....but it's completely curled...looks more like a REALLY long sock..... I tried blocking it a couple of times and then realized that it wouldn't work because the yarn is half acrylic.....is there a stitch I can do when working with non natural fibers so it will stay flat? It seems like I've read that there was...but I can't remember where I read it or what stitch it was.

You can knit the whole thing in garter stitch or moss stitch, or just do a few stitches at each edge in those stitches. About 2cm wide minimum, I think. Or what about knitting the whole thing in ribbing?

Stockinette stitch (all knitted on one side & all purled on the other) will always curl like that, no matter what type of yarn - it's because of the shape of the stitches.

Garter, seed and moss stitches will lie flat. For garter stitch, just knit every row (remember, a purl is just the back side of a knit stitch). Your scarf will be kind of ridged-looking and more stretchy than stockinette.

For seed stitch, alternate knit and purl stitches. Start with an odd number of stitches and knit/purl the same way on both sides - i.e., always start and end with a knit stitch no matter which side you're on.

I don't think I've ever tried moss stitch, but I found these simple instructions:
Start with an even number of stitches.
Rows 1 and 2 - k1, p1 all the way across.
Rows 3 and 4 - p1, k1 all the way across.
Just keep repeating these four rows.
That sounds like it will make kind of a "double" seed stitch, kind of a 2x2 "check" instead of a 1x1.

Knitting the whole scarf ribbed will work too - a ribbed scarf will be narrower and stretchy from side to side.

Just to add, seed stitch is super attractive.

or knit your scarf in Stockinette stitch twice as wide as you want it, then just sew up the sides. This way you don't have a bad side and it won't curl up