Updated 9.29.2022

BASICS

1.) Original condition is very important, in both parts and finish, including decals. Restoring, in other words 'repainting', damages a great deal of the value that might have been there. Repainted bikes are harder to sell to collectors, no matter how good the paint job is... A good guide: if you choose to repaint your bike, do it for yourself, not for any enhancement of it's future selling price.

2.) The brand or bicycle frame maker should be well known; nostalgia drives most buyers. Sadly, even high quality workmanship means very little if it is an obscure make. Not fair, but true.

3.) Older is almost always better, but see #1

4.) "Fancier" models trump lower-in-the-range models. The higher the model within that maker's line, the more appeal the bike will have.

5.) Historical provenance can significantly increase monetary value -  BUT it must be proven, the seller must have valid original, confirmable documents that support claims. Without that, it is just hearsay and adds no value.

6.) It is difficult to predict what the selling price for your bike might end up being. On occasion, a particular bike might sell for a very high $ amount, but we cannot assume all similar models will match that high price.  To find out what a similar item has actually sold for (not just what was initially asked) check "sold items" in eBay Advanced Search.
    Also there is a section in BikeForums.net called "What's it worth; Appraisals & Inquiries". The opinions as expressed by its members vary significantly based upon where they live and their experiences. Be cautious in accepting the comments there.

7.) Owners often exaggerate their bike values (it must be an ego thing?) In the end, your bike is only worth what a specific person is willing to pay, right now, today. Anything other than that is just wishful thinking. Be realistic!

8.) If nicely asked and supplied with very good pictures (see #2 below), most vintage lightweight bicycle enthusiasts will give you an opinion/an educated guess of what your bike might sell for. It takes a little research to find those people. Unfortunately, as per the rules, the Classic Rendezvous Google forum members are not allowed to be asked "value".  But the individual members could be asked privately.

GETTING READY TO SELL:

1.)  Carefully, gently but scrupulously clean the bike; use a tooth brush, car cleaning products like Armorall or equivalent (no build-up in crevices...) Just as in selling a home or an automobile, a grubby  item will not appeal to most buyers. (There are some who prefer to leave the patina 100% untouched. Certainly if this a historical bike, like Gino Bartali's old bike, that makes sense. But, as with a nice object of any kind, clean & well adjusted trumps rough.)

2.) Many high quality digital pictures are needed, of whole the bike plus many details of frame, decals, and components. Find a very plain background and shoot on a slightly overcast day. (Avoid "scenic" backgrounds; grass, trees, seascapes, etc. and do not shoot outside on bright sunny days) Use natural light and no flash.  It's best to upload these pictures to a photo-hosting web site like Flickr, Google photos, Smugmug, etc. and then offer link to potential buyers. They can also be linked in some online selling sites. A secondary benefit is that good pictures can start discussions in online forums,  then stimulating interest in new potential buyers. Onlookers can learn & discuss your item, this then helping your selling effort.

3.) List and describe in detail the make , model and dimensions of every component part.

4.) Include precise physical dimensions of the frame. At minimum, include the seat tube length center-to-center and center-to-top, the top tube c-to-c, the bottom bracket height, the stand over height at center on top tube, the chain stay length and the fork rake or offset. Ask any cycling enthusiast to help if you do not understand this stuff.

WHERE TO SELL

1.) Person-to-Person
   - Through a local bike shop. There will likely be a very high commission because your used bike will take the space and staff time of one of their own new bikes.
   - Local/regional Swap Meet or Flea market.  Usually offering mostly unsophisticated buyers and very often a low selling price.
   - Online services like NextDoor, Craig's list and Facebook which all are purported to be local. Be cautious because often peopole outside the immediate area use these as well.

2.)  VIA Online Contact
     (Remember, these not only depend on very good pictures, but will include the cost and risk of shipping.)
   - BikeForums's Classics and Vintage SALE section:  Requires an upgraded ($) membership.
   - eBay:  Yes, it costs about 15% or so, but you get world wide exposure and millions of potential buyers - this simply cannot be matched by any other means. Start high and let the market tell you if that is not going to work. It costs a pittance to place an item up for auction; they get you when it sells.
   - Facebook: Has a number of pages where vintage bikes may be offered for sale, like Steel Is Real, Vintage bicycles UK, and others. 
   - The Classic and Antique Bicycle Exchange: covers a wide range of ty[pes and age bikes.
   - Our Classic Rendezvous Google group:  requires joining (free) to access the approx. 4000 members. The For Sale announcements can be posted only one time, must have pictures accompanying the offer and must include an 'up front' set price. Therefore, as with any serious attempt to sell something, quite a bit of preparation is necessary before posting.
 

                                           Best of luck!