Hi and welcome from outside St. Louis, Missouri.

Missour Star Quilt Company has a great tutorial on making pinwheels, would be the same as triangles. Check it out.

a very warm welcome from KY!

Hello and welcome from SW Iowa. Glad to have you here.

Hello and Welcome to the board :D:D:D
Anytime there are bias edges I starch the fabric heavily and handle it carefully. Those edges will stretch way more than those cut on the grain lines :wink:

There have been some good suggestions. My first quilt was all triangles (different stars). I learned a lot doing it. Some sort of sizing, starch, etc. Press, don't iron. You also might need to check your seams to make sure they are consistent. If you are not seaming straight things may not lay very flat. I know people who use a foundation like Thangles or paper piecing to get great triangular pieces. You might want to play around with a few of the ideas. I would start with seams and pressing since those are free.

I would also invest in a walking foot if you don't have one. They can really make a difference. Mine is built into my machine (if you have a Pfaff you probably already have one). Hope this helps.

Greetings from New Hampshire

Hello and welcome from an Iowa girl! Check Rhonda's (on the board) method of making HST. Often times I make my HST's a little bigger and then trim down to the right size.

Greetings from CA. If you are making HSTs (Half-square triangles) there is a different method which you can find in Rhonda's tutorial. It may work for you. Don't worry - those other shapes will be your friend soon.