Keep yarn slack from developing in my work as I perform a basic knit stitch I am a very novice knitter trying to do a small blanket with a basic knit stitch. I am working with 100% cotton yarn and I have 16 inch bamboo needles. I cast on fine and where I am getting stuck is on the knit stitch. I do the first stitch and as I pull the loop onto the second needle I develop this slack in my piece. between the two needles that worsens with each stitch. 

How do I fix this? 

UPDATE

Please see  the image below, I am developing slack after the first stitch that grows with each iteration. I have just pulled the loop off my non working needle. I make my loops fairly tight as well so I do not think the slack is coming from there. After I put my working needle through the leg in the knit direction I pull the thread through and I tighten the thread going towards my yarn ball. 

I am beginner but this is preventing me from even getting a scrap knit together let alone a real project. 

On the topic of yarn and needle size, I have really long needles and made the amateur move of just grabbing a set and throwing out the wrapping so I cannot give you a diameter either. The yarn brand is Sugar 'n Cream 100% cotton, it does not list a needle size on the package. 

Thank you for the advice thus far... I am determined to get something going eventually.
From the image you've shown it looks like you're on the first row of knitting after casting on, and it also looks like you've used a loop (a.k.a. backwards loop) cast-on method.

It's common to get an ever-increasing amount of slack on the first row when using this kind of cast-on. A loop cast-on is easy to do, but hard to do well because the tension used when casting on is fiddly. If you keep knitting this piece the knit stitches will even out, but they might not even out completely.

I recommend starting with a long tail cast-on. It will take a little longer to get the hang of, but you won't have the slack problem.