Here is a tip I've discovered while making crochet clothing.
I know there is debate on how to sew your seams and it the seams go to the inside of the garment like when you machine sew or to the outside.
I'm not here to take up the debate, personally whatever works for you is the right way to do it.
I personally like to hand sew with maching yarn in what my mother always called a whip stitch.
You simply place to two edges together and sew through them, taking small stitches.
As in the above photo
The problem I come across when I do this, it that the seams have a tendency to stand out, or be raised up off the garments surface.
When working with a heavier yarn it doesn't seem to show as much as it does with a light yarn like this Lacette.
My solution is to wet press the seams. I place my iron on the cotton setting, let it warm up. I then lay a damp cloth over the seam and place the hot iron on it. A count to thirty and the iron is lifted. This makes the seam lay flat, more like it is part of the crochet garment and not an obvious indicator where it was sewn together.
I don't know if you can see the results on the above photo clearly, but the center seam and bottom seam of the insert have been pressed in this manner while the top seam of the insert hasn't.
Here the skirt has been completely pressed.