Thread/yarn thickness and hooks

 Thread comes in several weights. I have samples here of 5, 10, and 30. I usually use size 10 and a 00 hook. Usually, patterns call for a size 5 or 6 hook. I crochet so tightly that I have to use a bigger hook. When I make a gauge swatch, I find that I have to use a hook 1 to 4 sizes larger than the pattern calls for because I crochet so tightly.

 Compare hook sizes: 00, 9 and 13.

 Embroidery floss is just a bit thicker than 10 weight thread, and a bit thinner than 5 weight thread. A size 00 hook worked just fine.

 I've never used 30 weight thread. All that I have is left over from my grandmother. She used it to make flowers and edgings for handkerchiefs.

 I've bought size 5 by mistake. It makes lovely ornaments. It takes glue well to be very stiff when finished.

 Sport weight yarn for lighter weight sweaters and baby items. I use g or h hooks.

 Worsted weight yarn, I, j, or k hooks, only because I crochet so tightly.

Plarn. G or h hook. You might need a size or 2 smaller.
You'll know what size to use after making a few gauge swatches.