I want to convert polygons into points using QGIS.
I know how it's done in ArcGIS Desktop.
You can do polygon to centroid in QGIS using:
Vector - Geometry Tools - Polygon Centroids
You can do polygon to border nodes in QGIS using:
Vector - Geometry Tools - Nodes extraction
If you want to decide on your own point spacing, you can use the Sextante Toolbox with SAGA functionality activated (you'll need to install saga - www.saga-gis.org/ - and specify the installation path in sextante). Use the 'polygons to line' geoalgoritm followed by the 'line to points' one. You can create a model in sextante that combines these into one step as well.
Note: you have to make sure you install the right version of SAGA - I think its 2.0.8
If you want to convert polygon to point using QGIS. Then use
Vector > Analysis Tools > Mean Coordinate.