Now that the disclaimer is out of the way...*LOL*...First I mark darts. My favorite method is to use a tracing wheel and tracing paper. Now if you haven't used tracing paper in awhile it is soooo much better than the stuff I used when I first learned to sew...y'know that wax stuff that took the "all powerful cleanser" to remove the markings from your garment! I use Dritz tracing paper probably because I can get it in the garment district at Steinlauf and Stoller, where I purchase most of my sewing notions.
After marking them, I usually sew my darts in before serge finishing the edges of my garment. I use to serge finish all the pieces (one big sergefest) before I started any construction on the garment but I have noticed that in the last year & a half that method has gone by the wayside. I think that got phased out right along with my fast, faster, fastest sewing methods.
I sew the dart by starting about a half inch in from the cut edge, sew a few stitches forward and then sew in reverse to the edge. At the edge I sew forward to the point. About a half inch from the point I shorten my stitch length to really small baby stitches (1.0 on my Janome 8000) to the end, this locks the stitches without having to backstitch. Do I always remember to do this - noooooo - *LOL* Hey I gotta be real! But most times I do...and when I don't it's because that little 7th grade girl who learned to sew kicks in and I backstitch! However, my preferred method is to shorten the stitch.
Next, cut the threads...yeah, I'm being real basic here! Then I use my 6" shears to cut the top of the dart open. Another disclaimer, I only use this technique when lining a garment. Why?? Because I want the dart to lie as flat as possible on the fashion fabric when I add the lining to it. Sometimes I add a dart to the lining and sometimes I cut the lining from the fashion fabric piece after the dart has already been sewn but in either instances, I want those two pieces of fabric loving up against each other not fighting against each other.
If I'm not lining the garment, the dart is pressed down against the fabric. I don't cut it open because I am not going to attempt to serge finish the edges and possibly cut into my fabric with the serger knife as I get closer to the point. I also don't like having the additional thread in the dart.
Here is the most important part of dart making to me ~ outside of careful marking ~ pressing it flat and open. I can not impress upon you enough that you should not press a dart open or to the side on a flat ironing board. Please, please, please use your ham or your seam roll...whichever pressing tool you own...though I prefer my ham because you can get a really good press on a curved seam on your ham! Also, do not forget to use your pressing cloth. I have ruined many a piece of fabric from being anxious and not covering the dart with the pressing cloth first. After it is pressed (not ironed) flat, I flip the piece over and press with the pressing cloth on the right side to prevent any dimpling that may occur at the dart point.
I realize that these are simple tips but I've found that sometimes reading someone else's method of doing a "simple" sewing technique has upped my game and taught me something new. And since I ascribe to the always get better idea of sewing, hopefully something that I've shared with you about how I sew darts, will help you sew better darts too!