all good advice, especially the info on avoiding that bridge on Roosevelt Island - use ONLY the western side of the island.
The control channel (commercials) for the East River is Chanel 10 .... Listen in to hear the commercials 'check in' to 'control' for what is 'stacking up' and waiting for slack. When moving, keep your VHF on Ch 13 ... and TALK to them if anything looks 'doubtful' as the tow boats can sometimes wildly 'swing' in a following current. A jack-knifed tow is not 'fun' to watch, especially if close.
Going south I like to stage at City Island / Throgs Neck to be sure to be AT the Hell Gate precisely AT slack (for a mill pond ride through 'the gate') .... although you may have to wait if there's a crowd of 'commercials' waiting to go through. Be wary of the small sand scows, etc. crossing the river in the vicinity of 'the Brothers' - TALK to them to keep things 'clear'.
Do have your camera ready - its a great ride.
Staging at City Island makes it much much easier to time everything. The simplest way toil time everything is to look at any current chart and time your departure from City Island at, or up to about 90 minutes AFTER the current changes to ebb westward towards the city (but defiantly not a minute before or you'll ride the wrong edge of the wave and be really slow). This will put you on the ebb current which you will be able to ride all the way to NJ.
If you leave later than 90 minutes after the ebb current starts you may run into the start of the flood around the Narrows and be fighting current while dodging some large ships.
If you leave even a few minutes before the current swings, you'll likely ride into the last of the flood current the entire way through. I got there about 40 minutes early the last time because the wind and rains had delayed the ebb a bit, so I just dropped anchor, made a pot of coffee, and waited until I saw the current swing me towards the city, and then I resumed course.
On a J/109 delivery I once managed to time it flawlessly and get pushed by the current fall the way rom Larchmont to Sandy hook, then went down the NJ coast (no significant tidal current there), and caught the flood up into the Delaware around Cape May, which we ride all the way up to the inlet to the C&D canal where the currents split, and rode the ebb through the C&D and into the Chesapeake and nearly into Annapolis, before seeing any detectable current on the bow... dock to dock was 42 hours IIRC.