Building on Windows

Steps:

runprebuild.bat
Load OpenSim.sln into Visual Studio .NET and build the solution.
chdir bin
copy OpenSim.ini.example to OpenSim.ini and other appropriate files in bin/config-include
run OpenSim.exe

Building on Linux / Mac

Prereqs:

Mono > 5.0
On some Linux distributions you may need to install additional packages.
msbuild or xbuild if still supported by the mono version
See http://opensimulator.org/wiki/Dependencies for more information.

From the distribution type:

./runprebuild.sh
type msbuild or xbuild
cd bin
copy OpenSim.ini.example to OpenSim.ini and other appropriate files in bin/config-include
review and change those ini files according to your needs
windows: execute opensim.exe or opensim32.exe for small regions
linux: run ./opensim.sh
msbuild (xbuild) option switches
- clean: msbuild /target:clean
- debug: (default) msbuild /property:Configuration=Debug
- release: msbuild /property:Configuration=Release

References

Helpful resources:

http://opensimulator.org/wiki/Build_Instructions