Using a splitting maul
When it comes to splitting hardwood a splitting maul is essentially a mix of splitting axe and sledgehammer. They are normally heavier than normal splitting axes but the added few pounds makes the job easier on you. The axe side is used for chopping wood not splitting it. Do not use this side. Essentially what you want to do is use the maul side to drive a splitting wedge into your wood. This means you can get it to go with the grain of the wood so its a much easier job for you and repeat until the wood splits.
Length of wood
Most stoves only take wood of about 20 to 50 cm. to save time make sure you cut your wood to size before trying to split it. The added benefit of this is the shorter the log is the easier it will split.
Set up a chopping block
This is normally a large section of a former tree and this is where you will put your wood to split it. This helps with swinging your axe and causing less strain on your back. The block shouldn't be high or low enough for ricochets to be dangerous in case of a glancing blow.