You know it is always tough that to study organic reaction without a simple mistake. There is no trick way to study them fast. But there is an easy way to remember some of the reactions. Study the various type of catalysts. Yep, if you study them you can learn some of tge reactions For eg : if you are use aquous NaOH or aquous KOH then the compound may undergo substitution reaction to replace with -OH group or convert haloalkanes into alcohols
CH3CH2Cl + aq.NaOH/aq.KOH -> CH3CH2OH
But if you are using alcohilc solution instead of aquous solution of KOH then the haloalkanes converted into alkenes
CH3CH2Cl + alc.KOH -> CH3CH=CH2.