Pattern Mixing 101
Tip 1
Its always important to have an idea of what patterns you like or would like to wear! The more you like them the more you will like wearing them!
Stuck on this step?
Try creating a Pinterest board of any and all outfits, pattern, and colors you like! You will fin d patterns in your saves and start finding clothes similar to them.
What patterns do you love? 
Tip 2
Finding Similarities in Different Garments
If you have successfully found pieces you love try finding similarities between the garments. Look for texture similarities, this will give your outfit a cohesive look! Texture is just one example of similarities, others include and aren't limited to; color (saturation, hue, etc.), silhouette (boxy or slim?)
ExperimentationTip 3
Sometimes you never know what might go together so this is when you can have fun and just try a variety of different combinations until you find an outfit you love! This can take as long or as little as needed but this is the time for you to really explore what YOU like. You never know what might work. So just have fun!
DocumentTip 4
Take photos, and lots of them! If yo have documentation of previous outfits you loved it will be easier to make more outfits just like it in the future.
And there is nothing wrong with repeating outfits, if you felt confident in an outfit before wear it again!