[debuchak]

Hey guys..
How are solid-solid reactions supposed to be carried out.I'm interested in the reaction Ba(OH)2.8H2O (s) + 2 NH4SCN (s) --> Ba(SCN)2(s) + 10 H2O (l) + 2 NH3 (g)
am i supposed to dissolve the reactants in water first and create a reaction mixture? or something else?

[enahs]

Typically, yes.

However, sometimes there are other methods. For instance, the barium hydroxide octahydrate has a melting point of ~78C. It is possible that if you heat it up to make it a liquid the other compound could be soluble in it, and a reaction could then occur (might not be the once you expect) . That is however not the case for this one, it is just another example of ways we make reactions occur.
 
This is a very common endothermic reaction demonstration. Just mix them in water and it will happen.