To max out your skills in Create a Fighter mode, preview a fighter and then toggle his stats on and then off. Select him and choose "Customize Attributes" to get 3024 points. Select "Finished" and after the game saves go back and repeat the process until all skills are at 100.
Enter "Create A Fighter" mode, then select"Load Fighter". Highlight a fighter and press TRIANGLE to preview him. After your fighter loads, press A to display his stats and press A again to hide them. Press A to load your fighter, then edit his "Fighter Skills". The previous stats will remain the same and you will also have an extra 3,024 points to spend on skills. Use them, then back out to the "Finished" option and select it. After the game saves, go back to "Create A Fighter" mode and repeat the process as many times as desired. Note: The "Strength", "Speed", and "Cardio" values cannot be raised with this trick. This also cannot be done in Career mode.
In Career Mode, you can go into a Training Camp session with any amount of stamina and still begin the Camp Session with 100% stamina. Simply go to "Learn" and watch your training partner perform two of the tasks on the list. When you go to start the Camp session, you'll have a completely full stamina bar. This is perfect for sneaking in an extra sparring session before Training Camp without any penalty to your stamina.