I like SQuirreL SQL Client, and NetBeans is very useful; but more often, I just fire up the built-in org.h2.tools.Server and browse port 8082:
$ java -cp /opt/h2/bin/h2.jar org.h2.tools.Server -help
Starts the H2 Console (web-) server, TCP, and PG server.
Usage: java org.h2.tools.Server
When running without options, -tcp, -web, -browser and -pg are started.
Options are case sensitive. Supported options are:
[-help] or [-?] Print the list of options
[-web] Start the web server with the H2 Console
[-webAllowOthers] Allow other computers to connect - see below
[-webPort ] The port (default: 8082)
[-webSSL] Use encrypted (HTTPS) connections
[-browser] Start a browser and open a page to connect to the web server
[-tcp] Start the TCP server
[-tcpAllowOthers] Allow other computers to connect - see below
[-tcpPort ] The port (default: 9092)
[-tcpSSL] Use encrypted (SSL) connections
[-tcpPassword ] The password for shutting down a TCP server
[-tcpShutdown ""] Stop the TCP server; example: tcp://localhost:9094
[-tcpShutdownForce] Do not wait until all connections are closed
[-pg] Start the PG server
[-pgAllowOthers] Allow other computers to connect - see below
[-pgPort ] The port (default: 5435)
[-baseDir ] The base directory for H2 databases; for all servers
[-ifExists] Only existing databases may be opened; for all servers
[-trace] Print additional trace information; for all servers
