The decision to enter into a fence is subject to many variables that are dynamic and need to be weighed at the time of execution. You should consider volatility, skew, upcoming earnings/dividends, recent appreciation/depreciation, purchase price, reason and time frame for hedging the position, etc.
For instance, if vol is bid on earnings but you're still bullish and want to maintain upside, then consider an aggressive put with a further OTM call but overall lowing your hedging cost. If you are neutral the share price with no expected announcements then consider 10-15% OTM zero-cost to allow peace of mind. If you're bearish then consider 0-5% OTM zero- or low-cost.
There's no black and white way to enter a fence. You can do zero-cost, low-cost, or collect a premium.