Use a splitter like this: RCA VH48 Splitter (3-way) they're only a couple bucks, most brands are good enough. Keep your cable runs short as possible, and use RG6 cable to minimize loss. If you split too many times you may require an amplifier.
You loose between 3.5-4dB of signal everytime the signal is split. The first time the signal is split it drops 4 db, the second time it would be 8 dB. On a three way there is one outlet that has 4dB of loss and two that have 8dB of loss. A 4 way has 8dB of loss on all 4 outlets. An 8 way has around 12dB of loss. To figure the size of amp that you need to preserve your antenna's signal, figure 1dB for every 18-20 feet of cable, plus the loss from the splitters, then allow a few dB for other losses.
If you have good strong signals in your area, you may not need an amp. Try without the amp first. If you can't get good signal on all of your TVs then size and add a good quality low noise amp (less than 3dB of noise, quieter is better).