One more on the Semi-Slav -- just an introduction, there is a lot of theory to learn in some lines! 
Chess Tips
| MIDDLEGAME TIPS: |
* Preserve your options. Do what is required - whether a retreat or an attack - but don't burn your bridges unnecessarily. Squeeze your opponent's options - this is hard for them to sit still for, and they may lash out without heed for the dangers. |