Online Oman visa application is not mandatory contrary to all recent news in media. However e-visa can be obtained to facilitate easy processing at the boarder. 

Take few quick steps to apply online, visit:

https://evisa.rop.gov.om/home

Apply for tourist visa>Register new user>Login>Apply for Unsponsored visa>Follow instructions and make a payment

Currently cheapest available tourist visa is 5 Omani rials (50 aed) valid for 10 days stay in oman, Visa type 26A. For citizens of New Zealand visa type 26C and South korea 26D, both free of charge. Visa types and prices can be changed, suitable options always to be checked on Oman immigration website.

Note: Passport and photo upload size should NOT exceed 512kb each.

Once visa is approved you will receive it to registered email, visa MUST be printed for a visa run