What methods do we know about proving-disproving existence of rational points on surfaces of general type?
I was recently asked. My gut answer was- 'nothing'.



Surfaces of general type
Usually nothing, as you guessed $-$ though you might get lucky:


i) There might be a local obstruction (e.g. no rational points on the
twisted Fermat sextic surfaces $x^6+y^6+z^6+t^6=0$ and $x^6+2y^6+4z^6=8t^6$).


ii) the surface, say $S$, may map to a curve with finitely many rational points.


iii) $S$ may be contained in an abelian variety, in which case Faltings II 
applies (the big example is symmetric squares of non-hyperelliptic curves).


[it's been noted that both (ii) and (iii) mean that $S$ has nontrivial 
Albanese variety.]


iv) finally $S$ may have nontrivial $\pi\_1$, in which case one can lift to 
unramified covers and try to apply (ii) or (iii). For example, if 
$C$ and $C'$ are curves of genus at least $2$ with involutions $\iota,\iota'$ 
at least one of which has no fixed points then we can prove 
$(C \times C') \, / \, (\iota,\iota')$ has finitely many rational points 
by applying (ii) or (iii) to finitely many twists of $C \times C'$.


In each of cases (ii), (iii), (iv), some further luck may be needed to 
find all rational points and prove that the list is complete.


