Most seam allowances on garments are 5/8" - you should have a mark on your sewing machine at that point.  Sew from wide to narrow when you can - that's usually from hem toward shoulder.  And just as it's important to press seams as you sew them in patchwork, it's true for garment sewing as well.  Most seams are pressed open unless otherwise instructed.  Clip inside curves to be able to press seams flat.