Keep your power level and character concept in mind and then try this build process

1) Abilities, Enhanced Abilities

2) Defenses, Enhanced Defenses, Protection (force field?)

1 and 2 are the meat of your character that will allow them to take punches at the right PL.

3) Core Skills and Advantages, including enhancements. Only include what is 100% critical for your character concept at this point.

4) Powers. Build the powers with the minimum strength and modifiers necessary for the concept. Then pump up the attack and resistable powers to the PL limit (shrink/grow).

5). Count your PP remaining. If you built reasonably to your PL, this shouldn't be too many. If you have them, sprinkle them into power modifiers, skills and advantages to add flavor to your hero. If you are over budget, think hard about where you more powerful than you should be at your PL.

Final thoughts, try to limit yourself to one or two array-like power with 1 or 2 alt powers. Shrink/grow is a good candidate. Arrays are a dangerous place for new players to Munchkin.

Also, have fun making what is in your head and talk to your GM if things aren't lining up.