I hope I have made the case for precise marking and I want you to make sure to read the great comments/advice under the last post. There are other methods and some good ones.
Myself I tend to old school, and that really hasn't let me down. It adds some character to your sewing, if that makes any sense to anyone else but me.
I should also self identify as someone who doesn't really like marking methods that involve lifting the fabric layers apart to mark on the wrong side, with pins or markers, but that is maybe me - I am never sure that location is not lost in that process.
The exception to this would be sometimes in using dressmaker's carbon paper (not real carbon paper, I tried that once when I was ten and used some of my dad's navy carbon paper on some orange fabric, it most definitely shows) and a tracing wheel to mark patch pocket placement.
The trick to using a tracing wheel of course is to pad under the fabric with say a magazine and use a layer of plastic wrap over the pattern piece so it doesn't shred the paper.
Of course the only value of marking lines on the wrong side of the fabric for something like a pocket you need to place on the right side, is if you then thread trace (this means make hand basting stitches along the traced lines - in effect transferring them to the right side) them.
I have to tell you it is pretty terrific to have those little pockets all made up and to be able to just lay them on the right side of the fronts fitting them exactly into shapes where they are meant to go. It turns a stressful and mistake prone job to a no-brainer.
So that's when I would use tracing paper and I admit it is limited.
Like I said I don't like moving around things too much when I mark and you have to do that to slide the tracing paper in between the layers. For pockets and a few important stitching lines I will do it, but that's it. This, and it may be just me, is why I also do not use a rotary cutter and mat to cut out. I don't have a mat that covers my whole cutting table and sliding the mat around underneath a large project is not me.
So back to marking.
If the marks are anything that are located in the seam allowance I make a little clip. I know there are notches out too on the pattern but my serger cuts those off when I serge that edges to finish seams before I start sewing, so I make little clips.
These would be the ends of darts for example, centre fronts and backs and construction notches that help you match pieces.
BTW do you all know that single notches are for the front of garments and that notches are added as they move back? The front of a sleeve will have a single notch to match to the single notch of the front armhole, and the back will have double notches to match to the back of the armhole. Centre back seams have three notches for example too.
Oh on the subject of random information do you also know that a standard North American tape measure is 5/8" wide (check yours to make sure) so you can use it to mark seam allowances.
I also have a few extra personal marking codes.
For instance I mark every fold line with a tiny cut out V rather than a clip in the seam allowance. This allows me to distinguish between the front foldline on a shirt for example, and centre front (which is where vertical buttonholes are place BTW).
It also means that when I am making a pleat or tuck I can look at my in seam allowance marks and know that I have to fold the v clips to the small clips to make the pleats.
2. Sometimes I use masking tape on the right side.
Masking tape goes on and off fabric without a mark. I put small pieces on the right side of fabrics where it is hard to tell the right from wrong side as soon as I cut out and I use it sometimes to make sure that details like flaps are on straight.
I also use it to mark buttonholes.
I use a pen to draw my buttonhole positions on one long piece ( I often save and re-use these pieces of masking tape for several projects), the beginning and end of each buttonhole, and place these next to centre front where I am actually going to be stitching the buttonholes.
Of course I sew beside and not through the tape. This is a pretty precise way to mark buttonholes and very easy.
3. Which brings me next to thread marks.
Listen it may take a little time but not really once you get used to it.
Thread marks have the enormous virtue of being able to be seen from both the right and wrong side of the fabric, can be made directly on the pattern piece without shifting anything and so are very accurate, and can be made in different coloured threads so you can distinguish different markings.
For instance I use one colour to mark dart points and another to mark start and stop stitching points or pocket placements etc.
The traditional way, and the way engrained in me, to mark is with tailor tacks.
Now I have to tell you I am appalled by the sort of instructions you get when you Google tailor tacks. Nearly all the instructions are, IMO, just wrong because they tell you to clip through the loop and then pull apart the fabric layers.
This will just leave you with short little pieces of thread that are going to come out and get lost, which will put you back to square one.
So here are my old school tailor tack instructions, improvised on a little fabric scrap I found in the rv and photographed on the picnic table outside. I didn't have a paper pattern piece to illustrate properly so you are going to have to imagine these tacks being made on a dot on the paper pattern piece.
Here goes, step one:
Thread your needle with a double thread and don't knot it. Imagine the above has a paper pattern piece on the fabric. Take a tiny stitch through the paper/fabric layers, in and out as above.
Pull the thread through and take another stitch over the last stitch, more or less like the stitch you just made above. Leave it loose so the loop is big enough to get your index finger through. Leave tails on either side a couple inches long at least. Cut the thread. In effect you are making a thread loop through your pattern/fabric that looks like a cursive "e"
Do not, repeat do not cut the loop open, you are going to want it closed so when you pull apart the fabric layers you have a good long tail of thread that won't come loose on the underside of the fabric and a secure loop on the upper layer of fabric. Off course you are going to want to eventually remove the pattern pieces from the fabric when you are done so use the sharp end of a needle to gently tear a slash in the pattern piece over the loop so you can liberate the pattern. When you pull apart the fabric layers, like I have done here, the loop will go flat against the fabric.
Here is what you will see on the right sides of the fabric when you pull the layers apart. Note the intact loop will keep the threads from pulling out when you do this.
Finally you clip the threads and there you have it, efficiently marked fabric with a tailor tack.
Hope this is helpful.