There is actually no such thing as a "high sell volume" or a "high buy volume". These terms semantically refer to the volume that is sold down to buyers and the volume that is bought up from the sellers respectively.
Irregardless of the level of volume the amount of money flowing into a stock must always be equals to the amount flowing out(you cant sell when there are no buyers and vice versa). Here are a few pointers on volume in regards to Technical Analysis.
1) The market is in gear and has no forecasting value when prices rise with volume. It would be deemed as a natural trend progression if the appreciation(price & volume) is consistent.
2) In a bullish context, volume usually leads prices. A new high in price that is not confirmed by volume should be regarded as a red flag(technical weakness)
3) A bearish breakdown from a price pattern, trend-line, or moving average on high volume is bearish and may confirm a trend reversal. If volume expands on the downside, the scenario would be deemed more severe as it tells us that sellers are becoming more motivated.
4) After a decline, when heavy volume with little price change is observed, we could interpret this as accumulation and that is normally a bullish factor.
It will be much clearer if we can relate technical volume with actual trading psychology, as to me, that is basically the premise of technical volume interpretation.