1. before you click search game button, slightly right top of the search button got "region" button, you click that and check your ping to the server you choosen. ie: SEA server. you see your ping good and only play dota. i believe anything below 100ms should be consider good. in my case, i always reboot modem until i get good ping ~86ms. each time reboot i will checked whatismyipaddress.com to see my line is connector to which tm server. sometime alor setar, sometime baling, sometime penang, sometime klang, etc. 

2. some online video really pull all the banwidth and made game ping spike up. ie: when i watch badminton live thru betting website, it really make game high ping. so just stop it. my case is adsl2 modem with 4mb line rm88; scenario2: bad thing of adsl2 modem whenever upload fully use, all download speed will be gg, game ping will be gg as well.

3. some time pc affected with auto loaded or terclick pop up ads, it will made my pc high ping not only in game but to all website. to check this, i always use this: CMD then type ping -t www.facebook.com (i prefer to use fb), if got timeout means affected by some kind of malware/virus. this is fixable to use system restore.

4. scenario 4, high ping cause by dota2 patch itself, i found this after most major patch (big file), and no matter what i tried, it does not improve. so after small patch came after 2-3 days and it fixed the high ping. but to narrow into this scenario is pretty annoying...