Determine the form of narration you would like to present to your audience. A story written in the first person seems to always speak directly to the reader, which can be distracting. First-person narratives also risk miring the story in lengthy monologues with very little dialogue or character interaction.
Narrate the main character's adventures from the outside: do not write as him, but as someone observing him. In the third-person limited narrative, the narrator has only the perspective and thoughts of the main character, but pronouns are kept to the third-person. In short, the narrator cannot interpret unspoken thoughts of other characters, but is still separate from the main character.
Consider using third-person omniscient narration. In omniscient narration, the external narrator does have access to other characters' thoughts. As Stuart Evers of the "Guardian" points out, a first-person narrator needs to be realistic and engaging at all times. Omniscient narration, however, allows you to move between characters for a fuller perspective. This can also be an easier perspective to write from, as you can reveal as much or as little about characters' motivations and thoughts as you require.
Make authoritative statements. If you find yourself writing "I" statements in early drafts of your academic essays, eliminate them with authoritative statements of fact. This is especially important in persuasive essays: you want your statements to be strong, as if they are facts, as long as you can back them up.
Attribute all facts to a source. Appealing to an authority on your topic helps to give your paper a more authoritative feel. Rather than including "I" statements or offering your opinion, extend your research to find someone or something that agrees with you. Quote or paraphrase from your sources, with proper citation, to give your argument strength.
Use opinions sparingly. Sometimes in academic writing, you will be asked to give your opinion or relate your own experience to the topic. In these situations, first-person narration is acceptable, but try not to weigh your paper down with it: it still gives an overly subjective feel to an otherwise objective work.