At this level, you can increase your flexibility level by stretching for 20-60 minutes 5 times a week. If it seems too long, you can include it into your workout programs.
Similar to levels 1 and 2, remember to start with a 5-10 minutes warm up by moving all your muscle groups in a rhythmic fashion. This gets blood flowing into your muscles and prepares them for your exercises.
Try to avoid bouncing so use the Static-Stretch method and also drag your stretches for 10-30 seconds.
You can try yoga early in the morning. It gives you the right kind of flexibility you need in your routines. You can buy a yoga tape or join a class. 20-60 minutes actually go by very fast when you have a structured routine.
Here, your trainer can do more for you to help strengthen your core and posture.
Irrespective of your level of fitness or training objectives, make sure you participate regularly in your exercise routines. This is the only way you will actually start to look and feel better. You can find more information about fitness at http://www.menshealth.com/fitness/new-bodybuilding-rules.
Having the right personal trainer to work with will make your training easier and enjoyable.