Q:

What Steps Should I Take to Troubleshoot My Gas Oven? 

I recently purchased a house, and it came with a gas oven.  I've never owned or used a gas oven before, and the oven takes an extremely long time to preheat (like hours).  I replaced the door gasket after reading up a bit online about common problems, but it still seems to heat very slowly. 
What are my next steps?  It does heat, so it seems like it's getting gas and all, and I'm planning to take the front off and give it a thorough cleaning, but I'm curious if there are any other "first look" steps I can take that might help before calling a specialist. 

A:

I'd start by checking the valve, make sure it's all the way open.   If the oven has a cook top, you can probably lift up the top and find the valve towards the back where the gas line comes out of the wall and into the oven. 
If the gas appears to be cycling on and off while the oven is heating, then perhaps it's a bad thermostat.   
Beyond that, perhaps there's a clog in the burner.   I've never cleaned a burner to know if it's a DIY job, so I'll defer to others for advice there. 
As always, when working on a gas appliance, be sure to turn the gas off first before taking things apart.