How do I analyze a replay in SC2 and show useful statistics?

As far as I know SC2 Gears is the best tool you can find out there. Here is a feature list (not complete):

• Replay search describes how can you search and manage StarCraft II replays.
• Replay analyzer describes what basic and statistical information and charts you can get from a StarCraft II replay.
• Multi-replay analysis describes what advanced statistics you can get from analyzing and gathering information from multiple replays at once.
• Name template engine describes how you can define name templates to dynamically name or rename your replays.
• Replay sharing describes how can you share your replays with a few clicks on different replay sites, and what are the requirements from replays sites to be included in Sc2gears.
• Public replay commenting describes the integrated public replay commenting system. Build order import describes how can you import and analyze Build orders in Sc2gears, and the exact format of the Build order text.