From playing the Windows Phone version I had a very low starting average of 14.
I found the quickest way to advance this is partly from the solution above. Start a new game. Use a site like this one:http://www.scrabble-solver.com/
If you don't have a 7 letter word, resign, like the other solution says, it won't count against you. Rematch. Repeat till you get a 7 letter word and get the bonus for clearing your rack. This should land you 50-80 points per turn.
For subsequent turns, I found it best to start spelling from the top Double Word (DW) tile downward, as it opens up more DW, DL, TL, and TW possibilities. If you can't get at least 20 points on subsequent moves, resign.
If you are having issues with folks that just are not playing, here is how to wipe the games from the board. Got to Date/Time on your PC and advance the date one week. Come back to Alphajax and choose "Their Turns", then click on the games, you will be offered the chance to force them to resign, as the game thinks at least a week has gone by since the game started. Swap your clock back when you are done and make some more games.
The points don't seem to count till the other player moves or resigns, so forcing resignation can boost your score very quickly.