Please share some tips on hanging multiple frames on a wall

Position the focal point of the group at eye level.

Nail a small nail on the wall as a guide, use a string and span the wall while using a level to ensure that it is straight and then tie to another nail on the opposite end. Use the string as a guide, drive the nail you want to use to hang your picture on and continue for as many pictures as you need. Adjust the picture's string with the level until you see that the picture is hanging balanced and not lopsided.