It all depends on the size of your product. As the greater the % of agarose helps resolve  small linear DNA. While lower  % gives better resolution and separation of higher molecular-weight bands.On average it is the recommended voltage is around 4–10 V/cm (distance between the  anode and cathode and not the length of the gel) in the gel electrophoresis unit.

I generally run my gels with gDNA at much lower voltage: 0.7% at 70-75 V for 1.5 - 2h.While for PCR products, I run them using a  1% at 80V.

We use TBE buffers (Tris-borate-EDTA) as it is a better conductive medium than TAE (Tris-acetate EDTA) so is less prone to overheating.

Cheers!

Thank you for your responses. I will use 70 V for 40-45 min @ 0.8% for gDNA and 1-1.2% for PCR products. I hope it will not affect the DNA bands.

I suggest to you you always try slow voltage utilize.It  is better for DNA separation.Normaly 0.8% agarose use in gel electrophoresis, it's completele depends on your size of DNA.

In general, gDNA is run on 0.8% agarose gel at 50 V, while PCR is done on 1-1.2, and in extreme cases, even 2% agarose gel at 50-70 V. In both cases, the gel is run until the loading dye runs about 3/4, or 4/5 of the gel. Good luck!

Well I used to use the following concentrations of agarose gels based upon how you narrow down your approach and the segment size:

DNA:  1% gel as the size of DNA is large so a dilute concentration is used

PCR: 2% gel as the size is a specific segment of DNA which you have amplified and not the whole DNA

RFLP: 3% gel as now you might have restricted segments which you want to capture.

Volts: The lower ones work good as you want good separation so start with 80-90 mvolts, then increase to max 120mV for a fast gel.

The gel percentage depends almost entirely on the size of the DNA you are trying to resolve.  There also other factors to consider such as if you are trying to look at very small size polymorphisms in a PCR or digest.  There are a number of resources on the web to help you choose, for eg:

https://worldwide.promega.com/resources/pubhub/enotes/what-percentage-agarose-is-needed-to-sufficiently-resolve-my-dna-sample/

http://www.genomics.agilent.com/files/Mobio/Nucleic%20Acids_Gel_Electrophoresis.pdf

For discriminating between two similar sized products in genotyping we have used agarose up to 3.5-4% (although it is debatable whether polyacrylamide might be better here).

I would also suggest moving over to Borate buffer electrphoresis.  You can run it at a much higer voltage without overheating and you arguably get better resolution.

See:

Brody, J. R. & Kern, S. E.  (2004): Sodium boric acid: a tris-free, cooler conductive medium for DNA electrophoresis. Biotechniques 36(2):214-215

Brody, J. R., Calhoun, E. S., Gallmeier, E., Creavalle, T. D., Kern, S. E. (2004): Ultra-fast high-resolution agarose electrophoresis of DNA and RNA using low-molarity conductive media. Biotechniques 37(4):598-602.

for PCR product , it works beautifully on 2% agarose at 45-50 V and1X TBE buffer for about one hour and can be well recognized from the well separated bands of the DNA ladder upon Uv visualization as well as the visual monitoring of the migration of the tracking dye. For extracted DNA, better run on 0.8-1% agarose on 1X TAE buffer at 70V

You have answered the question yourself. It should be anything between 0.8% to 1.2% depending on your experimental set-up.

For PCR product uses 1.2% agarose at 80-90mV for 60 to 70 minutes. I recommend used 0.5x TBE. 

For genomic DNA, I use 0.8% at 50 V for an hour. For PCR amplified DNA, it will depend upon the size of the product. I use 2.3% for 2 hours for the CO1 gene of fish genomic DNA. 

the pcr product size is generlly smaller than genomic DNA, so we efficiently separated them on 2-2.5% agarose at 50V for one hour using 1X TBE

Genomic DNA can be run at 1% for 1.5-2 hr  using 1x TAE buffer and depending of your decision,if just to check for the presence and integrity of DNA, so 1-1.5hr run time is enough. IF you run a MW ladder with the samples you have to prolong the time  to 2.5 to ensure good separation of the ladder bands

Thanks to you all.

For genomic DNA - 0.8% Agarose gels

For PCR product- 1.4% Agarose gels ( ISSR MARKER}

Thanks to you all for suggestions. And, I used 1kb ladder for PCR products, 1.2% agarose gel, 50V for 30 min, ladder doesn't open clearly in to discrete bands. I load PCR sample 3ul. and ladder volume 1.5ul. What should be the correct quantity and other requirements of ladder to be used and volume of sample also? I am checking gradient PCR products for CURS genes and actin annealing with cDNA synthesized from turmeric rhizome. 

for ladder use 4-5 micro-liters, mix them with 3ul water and 2ul loading dye to make about 10 ul total volume to get nice bands in the gel. Extend the run time to 1.1 to 1.5 hours for the ladder to open well.

best sample volume is depending on DNA conc per sample. Generally use 5 ul of sample and treat it as for ladder.

I used 3:4 ratio of ladder and DEPC treated water and loaded 5 ul mix in to well at 70V for 45 minutes. It worked well. Thanks to you all.

chromosomal DNA =5V/ cm -1% agarose-1-2 hr

pcr product= 7V/cm-1.2 -2%agarose  (depend on product size)- 1.5-2 hr

Thanks to you all.