Raising money online will be a massive part of your fundraising efforts. Some people JUST focus on fundraising online as it's quick, relativley easy and you have a huge reach thanks now to social networks.
All it takes is for you to set up a fundraising page on a site such as GoGetFunding and then share the URL with friends and family.
What's of critical importance here is that you craft a great message in your fundraising campaign that really explains what you are raising money for and how the money will be used. Many sites also allow you to offer thoughtful rewards in exchange for donations and this has helped many fundraisers raise a lot of money.
The way you communicate your online fundraiser is also of critical importance.