You should raise your hands whenever you are making general Du’ah. The Prophet salla Allahu alaihi wa sallam had told us that Allah is generous and bashful and He is shy when His servant raises his hands (asking Allah) that Allah returns them empty handed.

I read is book of istisqa sahi bukhari that prophet p.b.u.h never raised his hands except dua of istisqa but in some hadith he used to like wars and witer etc so my question is do we raise hands for dua or not ?