Use of RG6 cables is recommended for cable connections.
Make sure all unused splitter outputs have terminators attached. Do not leave a splitter output without anything connected.
If you have a 4-way splitter then each of the outputs get 1/5th of the signal. If you cascade another 4-way splitter then each output gets 1/5th of the 1/5th signal = 1/25th of the original signal.
The antenna or cable signal to the house can usually be passively split 4 ways with a single 4-way splitter. To split a signal more than 4 ways a distribution amplifier is recommended.
Also note that your existing house wiring may have splitters hidden in the attic or crawl spaces.
A signal strength of 90% or higher is recommended for QAM operation, 80% minimum.
A signal strength of 80% or higher is recommended for OTA operation, 60% minimum.
If you have a cable modem then there are two options for digital cable: