Question: When asking an "ID My Bike" question what information about the bike should I include? 

Would a good "ID My Bike" question need all of the following or are there a few key things that would offer the best chance of an ID? Maybe something like - if these three things are included the chance of ID is 50/50. If these two things are added to that the chance goes up to 80%

**Pictures** (maybe some coaching on how to take good pictures) 

* every major frame joint
* all decals/logos/stamped names
* every component
* Other

**Words**

* Serial number
* Information about my current knowledge of the bike
* Links to information I have found so far
* Other

Answer: 
In order to ID a bike a question **must have**:

At least one clear picture.  

If there is no picture there is zero chance of providing an ID. The question will be closed.

The picture should be high resolution (any modern smart-phone will work)

In the picture the bike should be:  

 - well lit
 - right side up (sitting on it's wheels)  

 - of the whole bike  

 - from the chain side of the bike flat on. 

Pictures of the following are helpful:  

 - head badge ( on the front of the frame)  

 - logos  

 - decals  

 - distinctive frame features (lug work, square tubing, etc.) 

Other helpful information:  

 - Country in which the bike is located.  

 - What has already learned or is known about the bike.

Here is an example of a good picture.  

[![Required and Optional Pictures](https://i.stack.imgur.com/pXhFv.png)](https://i.stack.imgur.com/pXhFv.png)

This answer is a summary of the excellent answers provided by Argenti Apparatus and Criggie
This answer emphasizes a few things in other answers for clarity. In general, we ask for clear photographs of the entire bike, and preferably some close ups of select parts as well. Be aware that these are usually necessary *but not sufficient* to ID a manufacturer, model, and year. Identifying a manufacturer is easier, identifying model and year is harder.

Bicycle companies typically rely on decals, usually on the down tube at minimum, and head tube badges for branding. If you have those in the photo, you usually know who the bicycle *manufacturer* is. Of course, if those items are present, then the OP usually has the information to identify the manufacturer already. Nevertheless, not all head badges state the manufacturer clearly, but they can be recognized by enthusiasts. One example is Giant Bicycles' head tube badge. Naturally, some bicycles have had their decals and/or head badges removed.

Failing that, with steel bikes, the design of the frame lugs and fork crown lugs can sometimes be informative, although not all frames use lugged construction. Some other design elements on bikes in general can be distinctive, which is why Criggie mentioned things like unusual-looking dropouts, sometimes the seat cluster. As another example, some Colnago steel bicycles (e.g. Master and Master X-Lite) used star-shaped down tubes on the argument that they had higher torsional rigidity, and I don't believe anyone else used these. I think that these unusual design elements are more rare, however.

Identifying the *model* and manufacturing *year* of the bicycle can be harder. Sometimes, enthusiasts can match a paint scheme to a catalog, thus providing model and year - if someone posted a scanned catalog online, or if they collect catalogs, or if there's an example of the bike online, e.g. on Bicycle Blue Book (but that tends to cover more modern bikes). We can make guesses if we recognize the components or other frame features. For example, in the first photo Criggie posted, the components look like 9-speed Shimano 105, which was current in the early 2000s. The bike has a quill stem, rather than a threadless headset and stem, and these were less common on early 2000s bikes. So, it's possible the bike is from around the early 2000s, but it's also possible the components were refitted and the bike was from the 1990s.

It's been stated elsewhere, but the serial number is usually not helpful at all. Presenting the serial number alone is worthless, and it is quite possible that the question will get downvoted and maybe closed.