[ODE] Newbie Question on Numerical Integration Method

[James]

Hi, 

Some strange things are happening with my simulation and an engineering 
friend of mine suggested that it may be because my simulator is using 
Euler's method for stepwise numerical integration. He suggested I look into 
switching to another method, such as Runge-Kutta. 

I'm not an engineer and, alas, I don't precisely know what he's suggesting. 
I am wondering though, which method does ODE use by default? Is there a way 
to switch methods? Can this be the cause of weird behaviour such as 
accelerated 'wiggle' of bodies that should to be static? 

Thanks in advance,
James