I have been helping startups and medium business in their quest for ASO. Very recently, I have helped a Bikini Contest website in planning the ASO and overall marketing plan.
ASO will be done using specialised websites like App Annie and Sensor Tower.
Apart from Keyword Search for ASO, I can also help with On-page SEO activities:
Page Title Optimisation
Meta Tags Optimisation: Meta Description, Meta Keywords, Meta Robots, Schema Tags