Warping / Curling

Pretty much all my prints warp, especially when it comes to rectangular parts for the reprap.
I got a heated bed with pet film and use ABS juice to make it stick better. First layers squishes nicely.
I reduced the perimeter and fill speed to 30 and the heat after the first layer to 210, bed is at 110.
Still warps.

What do you do to prevent curling or warping?

Printing ABS with ABS juice I rarely see warping, I've found the print the first layer at a higher temperature generally to do more harm than good.
ABS juice is of no value if you are printing PLA.
How are you measuring your bed temperature, i.e. is that the actual bed temperature, or what the thermistor says it is?

Polygonhell,
I print ABS, and yes the bed is what the slicr is telling me. Just to the touch, the bed doesn't seam to be 110.
I was told to try at a higher hot end temp, such as 220 or 230.
220 is what I started with and it warped.
I will try soon again to get something printed with higer temp.

I'd use a thermometer on a multimeter to measure the temperature on the surface of the glass/tape. It really does need to be in the 110 degree range IME.
Yes generally putting the layers down hotter increased adhesion, I just find that I get a poor surface finish over the first few layers if I run the first layer only at an elevated temperature.

It's cooling to fast and contracting. Try to not have direct airflow over your bed.

Insulate your build platform, put some insulating or heat reflecting material directly under the heated bed, you will be amazed at how much this helps, also make sure your bed it up to temp 110-115C before you start printing, I notice that Pronterface will only wait for the Hot End temp to be at it's "GOAL", but not the bed, so waiting is the best medicine... lol

BAMCNC - you can add a M190 S### (if supported by your firmware, I use marlin) to your "start.gcode" and then it will also wait for the bed to get up to temp!

Apparently they only wait for the hot end temp to be reached because "it would be worrying for most users that the machine seems to sit idle for 20 minutes and then start automatically when it is ready"...

It's more of a worry printing at the wrong bed temp and having your first few parts end up a mess!