just_the_scraps_m'am

I came upon a number of odd blocks intended for a sample quilt, but somehow got tossed aside and buried under other projects. I would like to hear from those of you who make/have made/will make a quilt-top-as-you-go[with no pattern], what is the key is to make the blocks all appear cohesive?

any special techniques or processes you use? what works for you? thank you in advance for any help you can offer!