Use "Crop Circles" on the monster you Special Summoned with this card to keep a monster on the field .
This card works well with "Alien Kid" to destroy a monster they special summon.
This card is one of best cards to use in conjunction with "Code A Ancient Ruins". The Alien monster summoned through Mysterious Triangle is destroyed at the end of the turn, placing 1 "free" A-Counter on "Code A Ancient Ruins".
If you destroy your own Alien monster with "Mysterious Triangle" while "Code A Ancient Ruins" is on the field, at the end of the turn you will have 2 A-Counters on "Code A Ancient Ruins" - enough to summon an Alien monster next turn.
You can use "W Nebula Meteor" to protect "Alien Kid" or LIGHT Aliens you Special Summoned with "Mysterious Triangle". If you use it to save "Alien Kid", you can get a free draw out of it.