How could a marketing manager utilize modern marketing strategies?

Don't apply any techniques blindly, i would suggest first of all you must get into the DNA of the techniques you want to apply. Digital is growing but the medium is getting more dynamic day by day. Now, a days normal CPM, emailer etc strategies don't work as they used to be in initial stages. we have moved towards DMP i.e audience buying, programmatic and all. So, we should understand our end goal and then should apply the modern techniques which is suited best.

Make digital marketing as part of the overall marketing plan. Include social media and mobile marketing in your digital strategy. Figure out what you want to achieve from digital marketing to support the overall marketing objectives. Define your KPIs and follow them up with ongoing measurement and analysis. Analyse, tweak, analyse, tweak.