On level 1, allow all of the enemies to appear and 
 fly into formation without shooting any of them. 
 After the boss alien appears (the one that carries 
 the tractor beam attachment), you'll see a pulsar 
 similar to the ones the aliens appear from fly from 
 just above the boss alien to the middle-right of the 
 screen. Once it's gone by, shoot only the second alien 
 from the left in the bottom row of the formation. 
 A "Special" flag will appear just below where it was; 
 pick it up and you'll get a bonus ship.
 
 In Parsec 1, go up to the very front and wait for all the 
 bugs to come out. Then kill the 2nd bug from the left in 
 the bottom row to make the special flag appear. Now, when 
 the boss is coming down, move your ship and kill yourself 
 by touching it. Don't touch the blaster head, just the 
 boss. Your ship is turned into the blue one, and go get 
 the special flag.
 
 Another approach to the same situation: 
 At the start of the first round, push straight up until 
 you stop. DON'T shoot! Just sit there and let all the bugs 
 form. Right after the last row of bugs get into formation 
 a star will shoot from the top left side of the screen to 
 the bottom right. If you time this right you can get up to 
 5 shots on it. After about 10 hits on the star (it will 
 come out at random times during the game) it will transform 
 your ship into a new ship that can shoot 3 shots on the screen 
 ( 3 shots verticaly in a row ) instead of just 2.
 
 There used to be a book called "All about Namco" in 
 Japan years ago which included the tips, maps, and 
 everything of all Namco games. It had a few pages about 
 Gaplus and there was a table showing which bug you need to 
 kill to get the special flag. I don't remember exactly how 
 it goes, but it was kinda like this. If your score's 1000 
 and 100's digits are 00 when the new parsec begins (for 
 example, when your score is 0000, 10000, etc.), you need 
 to kill the second bug from the left in the bottom row. 
 If those 2 digits are 01 like 10100 and 20100, kill the 
 3rd bug from the left in the bottom row, etc. 03 is the 
 4th bug and so on. I think it goes all the way to the most 
 right one in the bottom row, then the 1st one to the left 
 in the second bottom row. When it gets to the most right in 
 the second bottom row, it comes down to the 1st one to the 
 left in the bottom row, then you're back at 00 (2nd bug just 
 like parsec 1).