How to set a dashboards on Grafana home page?

Grafana v4.6.3

In grafana click on the Grafana Menu, got to > Profile and under preferences you can set the Home Dashboard for yourself. For you organization you'll need to logon as an admin and under Grafana Menu > Main Org > Preferences you can set the home dashboard for your organization. This is for v4.6.3, but it should be the same in previous version.

Update for July 2020

Seeing as this answer is still getting up votes I've decided to update it to cover later versions of Grafana

Grafana versions 5.4.5, 6.7.3, 7.1.0

The same method works for all of these versions.

As ROOT says below: To set a dashboard as a default, or include it in the list of dashboards that can be used as the default, you need to favourite that dashboard as follows:

1. Open the dashboard you want as the default
2. Mark it as favourite dashboard
   • To do this click on the star icon in the dashboard header (in version 7+ the start is on the right-hand side)

Setting the default dashboard for yourself

To set a default dashboard for yourself do the following:

1. Select Preferences from the Profile menu (you'll find this toward the bottom of the Grafana menu bar on the left side of the screen)
2. In the Preferences view, under the Preferences group select the Home Dashboard you want as your default
3. Click on Save

Setting the default dashboard for a team

To set a default dashboard for a team you need admin rights. To set the default dashboard for a team:

1. Select Teams from the Configuration menu on Grafana menu bar
2. In the Teams view, select the team you want by clicking on it
3. In the Team view, select the Settings tab
4. Under the Preferences group select the Home Dashboard you want as your default
5. Click on Save

For an organization

To set the default dashboard for an organization you need admin rights, and you need to be in the Organization profile. You can set which organization profile you're in on the Profile menu.

To set the default dashboard for the organization do the following:

1. Select Preferences from the Configuration menu on the Grafana menu bar
2. In Preferences view, under the Preferences group select the Home Dashboard you want as your default
3. Click on Save

You can set via preferences, first login with admin user and then set home dashboard to whatever you want. Make sure you have starred it first before setting default one.