Sewing a straight line by hand

The Pros: It is easier to control the direction of the weave when sewing a straight line by hand.
The Cons: Keeping the fabrics aligned is quite challenging. The trick is pinning. Do a lot of pinning when needed. This way, you get to keep the fabrics in place as you weave the needle and thread. Just make sure you watch your fingers.

Sewing a straight line on a sewing machine

The Pros: Fastest way to stitch a piece of clothing.
The Cons: If you do not tightly hold and control the fabric, your garment may end up having stitches from dissimilar directions.

When sewing a straight line using a sewing machine, refer to the needle plate where the presserfoot rests. You will see four straight lines that correspond to hem measurements. These lines function as your guide too in making sure you are working on a straight line. Just keep the fabric aligned with any of the lines depending on your choice of hem measurement. You may use the pinning method as well to keep the fabrics in place in case you are doing layers. Another trick that may work for you is marking a straight line onto the fabric using a cloth marker. You can actually see the marker from the presserfoot so go over it precisely. And last but not the least of the sewing guidelines is an old adage “practice makes perfect.” I have learned from a local seamstress that the most efficient sewing practice for beginners is by practicing in a piece of paper. Draw lines in a piece of paper and go over it in a sewing machine with the needle on but without the thread. Continue practicing until you the dotted lines are accurately plotted onto your marker.