There are as many ways to migrate from Sharepoint to Alfresco as there are people who want to migrate from Sharepoint to Alfresco, which is to say, a lot.
You've given us very little to go on, but basically you have to worry about two things: (1) Getting stuff out of Sharepoint and (2) Getting stuff into Alfresco.
Sharepoint 2010 is quite old. You may find that tools like Apache ManifoldCF, which have Sharepoint connectors, don't work so well with Sharepoint 2010 (at least that was my experience). When that has been the case, I've used SPListX, a third-party tool, to do the export. It can handle sites, sub-sites, lists, and all of the metadata.
When metadata is not a concern (you just want the files, for example) there are other tools that expose SharePoint as a file share, so you could just drag-and-drop files out of SharePoint.
Now, to get the exported data into Alfresco, you have lots of options. If you are just moving files over you could just map an Alfresco CIFS or Alfresco WebDAV drive and do the copy. But many people want to move the files and the metadata. A common way to do that is the Bulk File System Import Tool. But you can also write your own import tool using a CMIS library from Apache Chemistry.
If you want to continue to use Sharepoint while you migrate to Alfresco, then you need something that can do continuous replication/synch. In that case you might look at something like Simflofy.
Hopefully this has given you some ideas. If you run into problems or have further questions, please create a very specific post with as much detail as you can provide and we'll try to help.
