My riding mower wnt start?

I pull the choke up all the way when the mower was not warm. The mower shut off. Then I tried to start it again and it just made some Putt-Putt noises. Then it shut off again. I replaced the battery and when I put it in the mower just smoked and got really hot. I cleaned off the spark plug with sand paper and tried it a gain and it did not make any noise. So my mom got a new spark plug and we didn't put it in yet. So please give me info on that. And this is an old wheel horse riding mower. So you do not need to sit on the seat to start it. Thank You !!!!!!