Launch PuTTY in UART mode with Raspberry Pi 3 default serial settings. Also set up a realistic text size for PuTTY. By default, it was ultra-tiny on my Linux Mint machine, so we change the font to a normal 12pt font. I figure most people should have the Ubuntu Mono font, so this should work well.

putty_uart_rpi3.sh

#! /bin/bash

###############################################################################
# File:   putty_uart_rpi3.sh
# Author: Alexander Hogen (https://github.com/ahogen)
#
# This script assumes you have added your user to the appropriate group(s)
# to access serial devices without sudo access. The "dialout" group comes
# to mind... To add yourself to "dialout", run the following command...
#
#    sudo usermod -a -G dialout YOUR_USER_NAME
#
# ... then you should be good to go (I hope).
#
# Launch PuTTY in UART mode with Raspberry Pi 3 default serial settings.
# Also set up a realistic text size for PuTTY. By default, it was ultra-tiny 
# on my Linux Mint machine, so we change the font to a normal 12pt font. I
# figure most people should have the Ubuntu Mono font, so this shoudl work
# well.
#
# Baud ........... 115200
# Bits ........... 8 bits
# Parity ......... none
# Stop bits ...... 1 bit
# Flow control ... none
#
# Size: 90 rows by 100 columns
# Scroll-back lines: 500
###############################################################################

putty /dev/ttyUSB0 -serial -sercfg 115200,8,n,1,N -fn "client:Ubuntu Mono 12" -geometry 90x100 -sl 500