Here are some recommendations for user-friendly mobile ad display based on best practices as of late 2015:

Q1: A good strategy is to focus on non-intrusive ad placements that don't disrupt the core user experience. Interstitial ads between major actions or views are better than pop-ups. Offer simple self-service ad setup via standard IAB ad units and sizes that integrate with major ad networks.

Q2: As an advertiser, we valued analytics on click-throughs, conversions, and demographic targeting options. Real-time dashboard reporting on campaign performance is also important for optimizing. Simplicity in setting budgets and scheduling was key since mobile is still emerging.

Q3: According to various studies at the time, native or content-based ad formats tended to be viewed most favorably by users. Specifically:
Native ads blended into the content flow
Small static banner ads (320x50) placed above or below content
interstitial full-screen ads loaded between pages or after a set time of app inactivity

Avoiding flashy pop-ups, auto-playing videos, or large takeover ads helped improve perceptions of being "less disruptive." Focus on relevance to the content being consumed for the highest engagement with users. Measure and optimize placement types over time based on metrics.