First things first. Go to a seasoned professional alterations person. Get referrals! I can't stress this enough.
Listen to the professionals at the salon. If they say size 8 is the size you need, order size 8...not size 6.
Plan on at least 3 fittings. One right away, one about 2-3 weeks before the wedding, and another the day you plan to leave the bridal salon with your dress (wedding week).
Ask the seamstress to double re-inforce all the elements. Do not back down on this. In other words, if she's planning on 1 hook & eye, ask for 2.
Snug is good, can't breathe is bad. Do not try to shove yourself into your dress. You will be uncomfortable, the attachments could give and break, bend or rip off. Trust me when I say its not worth it.
Fashion Tape, Safety Pins, and mini sewing kits can only do so much, especially if you have many layers, heavy fabrics, or a very long train.
The bustle that seems to work the best is the underbustle because it ties. Knots seem to stay put much better than sewn on hooks, loops, etc.
Ask the seamstress to number the ties so that whomever your designated bustle pro is, she can tie you up quickly and easily. Even if you have 27 bustle ties!
Ask for a ER plan- the wrist loop. Nobody wants to use it- but let me tell you something, if your bustle does fail, when the DJ plays "Shake your Tailfeather" and you are ready to boogie, if you don't have something to get the train off the ground you won't be shaking anything except your head!