While there are many excellent seforim today that compile Halacha l'maaseh, there is nothing that can replace having a personal relationship with a Rav who is also preferably a Posek. There is no simple, standard system to determine which opinion we pasken like, if there was it would be easy to be a Posek and there would be no machlokes in Halacha.
Which seforim are the most worthwhile learning depends on ones level of proficiency in learning. Even a beginner who is learning say Kitzur Shulchan Aruch should know that it is both comprehensive and easy to understand, and 95%+ of the halachos there are accepted by most Poskim. Even the cases we don't pasken like him, he is certainly a legitimate opinion to rely on.