I would like to know how you would summon synchro monsters lvl 10-12 e.g. shooting quasar dragon, celestial dragon, t.g. blade master and so on..

Fabled, Laval, T.G., etc.

as in the monster the spells and traps to do it

well there are multiple combinations to do it such as the laval rekindling combo or synchrons and as tono said fabled combinations are able to do it you just need to explore the deck options

go on an example

and in order

here is 16 ways to summon quasar in a junk doppel deck, https://www.youtube.com/watch?v=7UbiY_wKZsU
so as you can see the number of possible combinations is almost endless

HI im a master on qausar my fav. method is quickdraw and junk synchron

special quickdraw send level eater to the grave then special level eater special for 5 t.g junk warrior
play tuning bring in junk synchron summon junk synchron then go bring back level eater special armory arm then play one for on bring in spore make junk warrior level 4 special level eater synchro 2 draw 1 cards i usually send out a plant so special spore for 4 play quick draw again bring back level eater synchro with 4 spore and level 1 level eater level 5 t.g play your final reborn bring in spore synchro for your 6 with t.g to make your freind gaia synchro level 6 plus 4 junk warrior and level 2 formula synchron to make..... qausar..... then use armory arm to your bud qausar 5000 atk qausar negates everything inflicts damage to the atk and does 2 attacks..... so only 2 destruction or banish eff will kill qausar seeing how your qausar can beat some dumb 4000 atk qausar <:3

actually this is really simple

all u have to do to summon quaser is summon a synchro monster that is also a tuner monster (Formula Synchron) and 2 synchro monsters whos levels total plus the level of the tuner = 12

http://prntscr.com/1oq5ql
the result of a qauser deck

-_- i think she meant how to summon it with a strategy...

my strategy= ( 3 card combo)
from hand activate spell, molten transmission field
send tender of laval volcano and laval magma conneer
activate tender of laval volcanos effect from grace and send another tender of laval volcano from deck to grave and then again activate tender of laval volcano's effect againand send another laval magma conneer from deck to grave.

next from hand activate spell, rekindling and bring back all cards written above.

finally synchro summon TG hyper librarian first then synchro summon ally of justice catastor and then from hand special/normal summon boost warrior and synchro summon formula synchron and your. set to summon quaser WITH cards in your hand.

my qausar is stronger but your way is faster i like quickdraw qausar its fast and can summon qausar usually on my first move

laval quasar is the nub way to summon it

synchrons have multiple other options which makes them more versitle