Step 1: get rich
Step 2: start a religious cult and hire a PR man/woman
Step 3: secure some land and build statues of yourself
Step 4: promote nationalism and shut down any form of democracy while pushing your propaganda campaign
Step 5: sew seeds of doubt and incompetence within the current ruling class
Step 6: discredit all that oppose you
Step 7: have a parade to show off all your military weapons including chromed out cars (or bejeweled horses) and weaponry (even if they are fake weapons, just make them look real)
Step 8: take over current king's military through infiltration while getting all independent mercenaries/security to follow you
Step 9: take over all educational facilities (or build your own) while putting your picture up in all buildings.
Step 10: build as much weaponry as you can and pass them out to all that follow you
Step 11: have several emotional yet powerful speeches/rallies. Repeat several points over and over and get a slogan/chant. Get everyone worked up in group think
Step 12: start you takeover through force.
Step 13: rule through fear