How do I name GuiXT scripts and Input scripts?     

GuiXT scripts: GuiXT scripts are simple text files. They follow strict naming convention. GuiXT script names are based on the ABAP program name and four-digit screen number. A language is also included for various languages. Format: xxxxxxxxx.ldddd.txt ( xxxxxxx is the ABAP program name, l is the language and dddd is the screen number). For language independent GuiXT scripts ignore the language key.
For transaction MM01 first screen, the ABAP program name is SAPLMGMM and screen number is 60; the language is English. The GuiXT file name will be SAPLMGMM.E0060.txt
In normal practice please accept the name GuiXT and/or Script Editor Pro propose while saving the active screen.
Input scripts: Input scripts are simple text files as well. They do not have any restriction on what they can be named.