I used to live in Singapore. I used two strategies:
1 Avoid Sim Lim or anywhere near Orchard Road as they were geared to tourists - I used to go to somewhere like Ang Mo Kio Lorong 10 which is locals only.
2 DO start the conversation by explaining that you live there (flash your DBS card or residence card to prove it if necessary).
3 haggle like hell....then they know you are local
If you are ever going past Bike Haus on Bukit Timah road, say Hi to Colin Tan from Paul.
Ride it or milk it!