Case studies of work your agency has executed for other clients is always effective. Hopefully your case study will highlight work for a company closely related to your target.\n\nBusinesses are very interested in ROI - Return On Investment. Therefore, present metrics you've used to track previous campaigns, as well as the "win" your client realized.\n\nAs with all advertising, building a brand is important. Therefore, try to market your company in ways that highlight your brand attributes.\n\nRemember that in your case, you have at least two target audiences: future clients and future employees.
how does an Ad agency advertise itself?