OS?
Provide enough power (undervoltage causes instability).
Connect HDMI - if applicable (no cable present at boot will by default disable video output).
Connect peripheals?
edit/create in /boot
Example:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev update_config=1 country=CZ network={ ssid="YOURSSID" psk="YOURPASSWORD" scan_ssid=1 }
User: pi Password: raspberry
Python recomended, any language should be feasible though. Many libraries available (as usual with python https://xkcd.com/353/)
example of /etc/network/interfaces
auto wlan0 iface wlan0 inet static address {{ wlan_ip }} netmask 255.255.255.0 wireless-channel 48 wireless-essid crocs-raspi-net wireless-txpower 1 wireless-mode ad-hoc