Rhonda--both methods. If they are squares as in the nine patches and bars of the bookmarks I use the 3/4 inch squares or rectangles with a 1/4 inch seam allowance (love my 1/4 " foot--just got it this spring). Many of my HST are left over triangles from Flying geese, snowball blocks, or binding joins. I pair up 2 triangels--sew a narrow seam allowance (1/8-1/4"). Press and cut them to the closest size--ie 3/4, 1, 1 1/2--whatever.
I trim seam allowances to 1/8 inch (more or less). I've experimented with pressing seams open or to the side. Although the block has less bulk pressed open, it's easier for my hands if I press to the side. (I think I've milked too many cows in my life!) Also pressing to the side gives me more accuracy when I butt the seams together. Recently did the seamstress trick of grading the seams say 1/8 on one side and leaving 1/4 on the other--then pressed to the side. This may be a compromise solution for me.