Have you found a pattern yet? Some pattern books have little symbols (like this). These symbols (triangle, inverted triangle, circle and hourglass) match figure types and tell you that the garment looks good on this type, but not on anther (see “about figure flattery”).
Now that you’ve found a pattern that’s not too difficult (skirt or simple dress), it’s time to think of the next steps: fabric and fit.
The easiest fabrics to sew for beginners are cotton and cotton blends. Solids and prints. Stay away from stripes and plaids or any small print that repeats with less than 4 inches/10 cm. It is too difficult to match. Get a medium to heavy weight fabric - one that you’d see in a skirt.
I’d advise pre-shrinking any fabric for now. It is not necessary for 95% of modern fabrics, but better safe than sorry.
Most patterns have printed on the front piece the actual hip/waist/bust measurements of the completed garment. This allows for ease of movement and style.
If you are lucky, you won’t have to do any adjustments to the pattern for fit. However, if one of your measurements is one size and another is another size, go with the larger size. To pick some numbers out of the air, if you are a size 10 waist and a size 14 hips, and multiple sizes are on the same pattern, cut the pattern with 14 hips graduating down to 10 waist. If only one size is on the pattern, choose the larger size and make adjustments as you sew.
Places to make adjustments are seams and darts. Most US patterns have 5/8" (1.5 cm) seams. To make the garment bigger, you only have 3/8" (1 cm) per seam you can play with (you need at least 1/4" seam or run the risk of holes at the stress points). That is why everyone is telling you to cut big and sew down.
If you chose a dress pattern instead of a skirt, you have to pay attention to two other measurements - bust and back waist length. For the bust, just go up or down a size (when you are a more experienced sewer we can talk again about alterations to the pattern). For the back waist length, it is the measurement from the base of the neck to the natural waist. I am short-waisted - the measurement is about an inch shorter than “normal” - so in order to get a good fit I have to fold the pattern along the double lines printed right above the waistline before I pin it to the fabric. (Different patterns have different ways of showing the lines.) If you’re long-waisted, you have to cut the pattern, insert a scrap of paper, and tape it in place. These alterations are a pain in the ass to do, but it makes a huge difference in the fit.
As mentioned (I think) the sheet with the instructions usually has a diagram of the best way to lay out the pattern pieces. I cut out the pattern pieces on the lines completely with dull scissors before laying them on the fabric. (Paper is made out of WOOD, something that dulls my good, sharp scissors.) Others just approximate the pattern pieces, figuring scissors are cheap, and save the precision cutting for later.
There is an arrow printed on each pattern piece. Line the arrow up with the selvage/fold by measuring the distance from the closest edge to each end of the arrow and pinning it. There should be no more than 2 mm difference between the two measurements.
Measure twice, cut once.
It all sounds like too much work. And if you want to, you can skip most of these steps to get sewing faster. But they will result in a better fit and easier sewing if you try them.