Things you can do:

• Install StreetComplete, OsmAnd, Organic Maps or OSM Tracker, go out and map :) The first one is good because of you having to find what to map, it’ll show you quests to solve.
• Open OSM in a zone you know, click the edit button, and start armchair mapping :)
• Go over the HOT tasks manager and help with current tasks, like Greece’s flood or Marroco’s earthquake. This is slightly advanced, but mot much, they usually ask you to map roads and buildings.
• Use any of the many channels to contact your nearby community (check the wiki) and get local help.