|There are many steps to getting that great fit, it's not just luck.
After doing flat pattern adjustments and tissue fitting, there's the 1st muslin. You could hand or machine baste but I prefer to
Pin basting is taking pins, I find that short ones work best for this, you then pin at the seam line.
I pin baste with the side seams facing outwards so I can easily make adjustments. Other seams can be lapped or what ever is appropriate for that piece.
This process is infinitely easier done on a dress form, even one that isn't your exact size as it allows you to pin curves much easier. I don't really see how you can baste without one, maybe it's possible but I'd imagine a lot more difficult.
Try your garment on (carefully as this has the potential to hurt!)
and determine what needs to be altered. You can re-pin it and try again until it's right.
Note adjustments needed. Transfer to your pattern.
This is quite time consuming but you end up with a much better fit and no big surprises when you sew everything up.
I only learned of this technique after sewing decades and I wish I had known to do this along time ago. I would have had a lot more successes in my earlier years but I was always in a rush to get things made up fast. I must add that I have many wadders that could have been saved if I had only done this. These days I rarely have any.
By the way, I do teach this technique to my students. I have found that most students won't take the time to do the pattern alterations, muslins, basting (pin or hand) but then when something is all sewn up there is that looks of confusion as to "what went wrong?". It's almost always far too small.
Of course, I go over what is needed to get a good fit and I see eyes glazing over...
it's almost funny!
But it's my hope that there are PR members who will benefit from this info.
This is best if you can get someone to help you although I do this on myself.
For tops/dresses ~Start at the shoulders and make corrections there before you go to the next step. Then do your side seams and again make corrections.
Sorry, I do not have explicit step-by-step directions for this. I learned to do just by practicing and seeing what made sense.
You will quickly get the idea once you start doing this.
If you do not have a dressform, you now have a great reason to get one. This technique is best done using one. I'll pin baste on my form and then after it's all done and corrected, I try it on for one more fitting before I sew it up.
For pants~ if you have the real fit for pants, there are instructions on how to pin fit pants that are excellent.
good luck and give this a try. I think you will be delighted with the results!