There are many ways that you can help to improve the quality of OpenStreetMap data. After familiarizing yourself with OpenStreetMap features and tags, you can use a tool such as JOSM or iD to verify and if necessary correct the features in an area which you are intimately familiar with. For example, you might initially look at the area around where you live or work.
Most people will quickly grow beyond these familiar areas that they can check, and you will soon need a direction in order to make productive corrections and additions. A good starting point would be to look for a local User Group or Mapping Party. These will be taking on more substantial mapping projects, and will be able to direct you in the right direction. Perhaps a new housing area has been built, or the quality of mapping in a specific area needs a major overhaul.
Mapping parties can involve a large amount of time. They are not practical if you only have a few minutes here and there, or you cannot make their schedule. A good alternative is Map Roulette. Map Roulette is loaded up with a number of projects (“Challenges”) to work on. Each project typically has a large number of relatively simple tasks, often of a quality-control nature. For example, current US projects include one to verify the one-way tagging of highway ramps and connectors; and a project to verify Texas cemetery locations. The latter was due to the cemeteries being imported from a Texas State database which had not been well maintained. This resulted in a lot of cemeteries being marked in the wrong place or being marked when they had never actually been built. Each one has to be verified or corrected. The process cannot be automated. This is typical of a Map Roulette project: each individual task is quick and can often be completed in a minute or two, but it cannot be automated.
After examining a task, you can mark it as “false positive”, “skip” (e.g. if it is too difficult), or you can edit it with JOSM or iD.
So next time you have a few spare minutes, log in to MapRoulette, fire up JOSM and start working on one of the challenges!