You need to be analytically strong and understand financial concepts. The basic building block is understanding time value of money, discount rates, cash flows etc. Essentially, that will be your main job, to understand a firm's value. You'll have to say more on what you know so far (educational background etc) for me to dig deeper in this field.

Build your personal brand and portfolio. Start doing the work on a small level first and scale into the vision would be my answer. Option 2 find someone doing exactly what you want, offer value and land a mentor. Get connections and go the networking route.

You will need to acquire knowledge of core M&A practice areas preferably through some credible certification before starting your M&A consulting practice. You will also need to be aware of various deal sourcing platforms like Deal Stream, Deal Gate, Deal Nexus intralinks etc. You can also join M&A industry association/platform like Alliance of M&A Advisors for networking with peers and industry experts.

While in practice you will need to develop partnerships with other M&A Advisory firms, consultants and investment banks for deal sourcing. You will also need to establish links with institutional and strategic investors including PE Firms and Investment Management Companies including Hedge Funds. For this purpose you can use corporate finance research database like privateequityinfo.com. This will allow you to search and shortlist PE Firms and other Strategic Acquirers based on their investment criteria. You will also find the emails and contacts of their executives in that database.

Remember the only key to success in M&A Practice is your networking and industry contacts that will be of great help for you.