Just say three times and get greatest reward

Whoever asks for Paradise, three times:

[اللهم اني اسالك الجنة]

Paradise will say: "O Allah, admit him to Paradise."

And whoever asked to be saved from Hell, three times:

[اللهم أجرني من النار]

Hell will say: "O Allah, save him from Hell"

[Ibn Majah, Graded Sahih]