If you want to make something without too much second guessing, you’ll need a pattern.
Not all patterns are created equal. Some have questionable sewing instructions. Some have questionable drafting. Don’t be discouraged if you run into this. Most commercial patterns are fine.
Most patterns these days will have a few common elements.
Seam Allowance
It’s rare today to find a pattern that doesn’t have seam allowances included. However, it’s always good to check and see if it does, and if so, what the seam allowance is.
When I first started sewing, everything was 5/8″. But now I’m finding a lot of other options out there. 5/8″ and 1/4″ seam to be the most common. I see 1/4″ for knits and close-fitted garments.
I even have a pattern that has a 1/8″ seam allowance on a very specific part. (Yikes!).
Piece Alignment
Each pattern piece should have a grainline on it. This indicates how to line the pattern up on the fabric. The grain line is supposed to go in the same direction as the grain of the fabric.
On some patterns, they won’t have a grainline, instead, they will just have a fold line. It’s assumed the fold is on grain.
On some patterns they will have a DOGS line. That stands for “Direction of Greatest Stretch”. It’s often found on close-fit garments that are meant to be made out of a stretch fabric. If you use one of these, you get to test your skills at measuring stretch.
Other Pattern Markings
Other common pattern markings are things like notches, or circles and squares.
All of these markings are used to line up the pattern with another piece or to indicate starting or stopping of sewing.
Typically the notch will just be used for lining up pattern pieces.
But the circles and squares can indicate where two points should meet, or where to start or stop sewing.
On garments, you might have a center front line or a center back line.
You might also have markings for placement of patch pockets, buttons or button holes, or other embellishments.
There may also be instructions on where to gather, or ease fabric.
And each pattern piece should also indicate how many pieces you should cut from each piece in each type of fabric (fashion or main fabric, lining, interfacing etc).
I have three in-depth articles on patterns.
How to read a commercial pattern – this goes in to common markings and instructions in commercial patterns. (Many independent patterns also follow the same standards.)
Using Commercial Sewing Patterns covers how to trace patterns and use the patterns without destroying the original
And lastly, 3 Rules for Laying Out Patterns and Cutting Fabric goes into how to actually cut your fabric using a pattern.