Best way to build muscle? (arms and chest)?

Everyone says something different. What is the best way to build muscle in my arms and chest (especially arms) When I do more sets of 12-15 with lighter weight, I feel my muscles tiring but Im not seeing results. When I do 6-8 sets with heavier weight, my muscles arent getting tired, they just arent capable of lifting anymore. What is the best approach to TRULY build muscle, because I cant figure it out and get the results that Im striving for.