It goes like this: 
 if(a > 0){ 
     //one or two lines simple code (updated) 
    if( b > 10 ){ 
       //one or two lines simple code (updated) 
       if(c > 0) { 
          //complex code 
      } 
    } 
} 
 
See the arrowhead above ? 
 
Rather I prefer: 
if (a < 1 ){ 
  return 
} 
if (b < 11 ){ 
  return 
}   
if (c < 1 ){ 
  return 
}   
//complex code 
 
BUT ! 
Steve Barnes below has an even better solution that takes care of the early returns 
 
bool OK = FALSE; 
OK = (a > 0);  // Comment why 
OK &= (b > 10); // Comment why 
OK &= (c > 0);  // Comment why 
if OK { // Good to go 
    // Do your stuff 
} 
return;