Like Lactose wrote, there are loads of ways of doing it. It'd probably be best for you to start out using some standard format like XML or JSON, instead of inventing your own text or binary format. Then you'd have a file like
<type class="MyAwesomeObject" />
<position x="100.023" y="39.5" z="-882" />
<rotation z="23" />
Your language of choice will most likely an API for easily serializing/deserializing objects to text like this.
Depending on the size of your level, you can either keep it in memory as a flat list of objects like this, or you might need a spatial partitioning datastructure, like a simple 2d array or a quadtree, to contain the objects, so you dont have to traverse them all in order to touch the objects in a smaller area.