Star with an idea and get pixelling. Because you're new and likely to make errors in the basics of pixelart I suggest you make a WIP thread and ask questions then update and ask more questions and keep doing that and focus on what pixelart is all about instead of trying to make a great piece of the bat. When you first start actually laying pixels down and you decide on a canvas size you want to make >>> REDUCE BY 50%!!! >>> the begin.
Read the noobtorial and cure's pixelart threads in the resource section for a general background on the basics.