Look at 1st round and identify the position that will both have value and improve a need.
At #19 the 2 positions of value are WR (Marqise Lee, Brandin Cooks, Odell Beckham) & LB (CJ Mosley, Ryan Shazier).
IMO LB is both better value and need.
Thereafter I would identify players who fit current scheme and have dropped due to; position depth, poor combine, recent injury or size, height, length issues. Certain players with character issues such as Kelvin Benjamin, Colt Lyerla, Jeremy Hill, Seantrel Henderson etc would be off my board.
Players I like 2nd round on are:-
Marqise Lee WR, Jason Verrett CB, Jace Amaro TE, Cyrus Koundijio OT, Austin Seferian-Jenkins TE, Antonio Richardson OT, Travis Swanson C, Jarvis Landry WR, Jack Mewhort OT, Anthony Johnson DT, Devonta Freeman RB, Daniel McCullers DT, Craig Loston S, Anthony Steen OG, James Hurst OT, Caraun Reid DT, Antone Exum CB, James Wilder Jr RB, Ryan Carrethers DT, Brandon Linder OG, Marion Grice RB, Bennett Jackson CB, Brett Smith QB.
IMO, San Diego drafted like this last year. Their biggest need and a position of strength last year was OT. They drafted DJ Fluker. In 2nd they snagged Manti Teo and Keenan Allen with 3rd, who both dropped due to various issues but no charachter concerns. That is 3 starters out of 6 picks.
This is how to draft!