The way I've gone is basically whatever to I-87 to I-88 (via a bit of I-90 W, which although it's a toll road is free between those two exits) to I-81 to I-70 to I-270 to I-495. How you get to I-87 depends on where in Vermont you start from; if in the northwest part of the state, US 7 to VT 22A to US 4 to NY 149 to US 9 works well. For centralish areas, catch US 4 and continue as above. For southern areas, VT 9 which becomes NY 7 is not unreasonable, if a bit hilly in places.
I-91 to I-84 is another possibility, albeit sometimes congested and with apparently everlasting construction.