Suggestions that have worked well for our Troop:

Pre-cook the pasta a night or two ahead of time. Drain and put into zip lock bags and refrigerate. This really speeds things along on dinner night.

Thank companies/individuals that have provided financial or material support on placemats. They are simply printed on 11x17 copy paper. It may be an additional fundraiser for advertising depending upon your (or your SE's) interpretation of BSA fundraising policies.

Think about what to do with leftovers. We send it to a local homeless shelter. We have also considered freezing for an easy camp meal but the shelter is glad to have it.

Good Luck!

Parcel out duties such that the boys are not just busing tables. Boys should be cooking, serving, welcoming, cashiering, entertaining (skits, anyone?) right along with the adults.
Make a display of activities, pictures and Scout memorablia in the entry hall.
Get the media involved. Pester the local TV and newspapers to come and see some "good news" to report. Lots of advance notice.
Taste test the menu a week before. Leave time to "correct" things.
Bake sale? Dessert included?
Make sure you invite the CO's IH and COR and get on their newsletter/ bulletin.
And everyone wear the Troop Tshirt (or class As? Spaghetti stains?) and hats.

have some decent background music. Goods donations too small for the silent auction can be used as random door prizes. Definitely have carryout containers.
Meat sauce adds to the costs; cheaper & nicer is to put 2 decently sized meatballs on the plate for those wanting the meat version. Some will not be able to eat tomato sauce that day (digestive upset or whatever). Be prepared to offer the noodles with a butter sauce & grated cheese. Have peanut butter, bread, strawbery and grape jams for the kids that suddenly won't eat the spaghetti. Having Scout displays has already been mentioned. If your service is slow, have some crayons & paper for the kids. Have racks for people to hang their coats
Whatever you do, don't place a nicely decorated, well bolted down tip jar near the exit.

If a unit would like to try the placemat thank you/advertising, I have added a free placemat template to my website under the fundraising heading.

www.thriftyscout.yolasite.com

Feel free to try it as part of your next fundraising dinner or breakfast.

Good Luck